Banshee jetting FAQ
Everything you ever wanted to know about Banshee jetting! While the specifics listed are based on the Banshee's stock carbs, the principals remain the same and are similar for other carbs (and anything else with a carb). I'd like to thank all the past and present members of BansheeHQ.com for all their valuable help and input. I've tried to cover as many carb issues as possible, from the most basic to the more complex, so some of you may want to skip ahead (go straight to Q#12 if you want to dial in your mains), and others are welcome to add anything that I've missed or have yet to learn.
First off, here's an excellent link to Carb Theory 101, showing the basics of what does what in the carb:
http://204.71.0.3/motoprof/moto/mcycle/carb101/carb101.html
Also, here's a link to Meat's page with some great carb info and
pics:
Next, here's the carb specs for a
bone stock
'87 and up Banshee:
Mikuni VM26SS roundslide
Pilot jet size:25
Needle:5N7
Needle clip:Middle (clip #3 of 5)
Main jets are standard Mikuni small hex mains, available from most bike shops, and come in increments of 10 (210 is one size larger than 200, etc.)
Pilot jets are Banshee-specific, only available from a dealer or a knowledgable shop, and are available in
increments of 2.5.
Yamaha pilot jet part numbers:
27.5 Pilot:260-14142-27
30 Pilot:260-14142-30
32.5 Pilot:260-14142-32
35 Pilot:260-14142-35
Now some basic q & a:
Q#1:Why is proper jetting important?
A#1:Depending on your priorities, proper jetting will get the most
power out of
your motor, and prevent premature wear (which can quickly lead to
failure on a
high-revving 2-stroke like the Banshee).
Q#2:What happens when my Banshee isn't
jetted
properly?
A#2:If the jetting is slightly lean or rich,
the most
you'll suffer is a loss of performance. However, if the jetting
is way
too lean or rich, your Banshee will overheat rapidly resulting in
melted or
seized pistons (which is the ultimate "bummer" for the 2-stroke
motor).
Q#3:What does "rich" and "lean"
mean?
A#3:Rich refers to having more fuel per
volume of air
in the intake charge entering the motor than the perfect combustion
ratio. Lean refers to having less fuel per volume of air than
optimum.
Q#4:So how do I know if I'm too rich or
lean?
A#4:Your best, most definitive means of
identifying a
rich or lean condition is by reading your spark plugs (see Q#37).
Eventually you'll get a good "feel" for the jetting of your own bike,
at least if you ride it often enough and hard enough.
Q#5:How do I correct a rich or lean
condition?
A#5:Jetting, of course. Jetting in
itself refers
to the process (mostly trial & error) of adjusting your carbs
to get as close as possible to the perfect air/fuel ratio.
Typically this
consists of changing the main jet to a larger (or smaller) size,
changing the
pilot jet size, adjusting the airscrews, and adjusting the needle clip
position. Sometimes it can involve adjusting the idle speed,
synchronizing the carbs, replacing the
needles, and
adjusting the float height. Don't worry,
it's
not as hard as it sounds!!! Most importantly, don't get
frustrated, take
your time, and don't be afraid to ask for help. Carbs
can be confusing, and nobody was born with the knowledge required to
tune a
single carb, let alone two of them.
If you have
some basic problem-solving and screwdriver-turning skills there's no
reason to
let anyone else touch your carbs, EVER!
Q#6:I think my jetting is lean or rich,
what do I
do?
A#6:First, make sure jetting is the problem
and not
something else; a Banshee can exhibit symptoms of rich jetting without
that
being the actual cause. For example, a dirty or clogged air
filter will
restrict airflow, resulting in a rich air/fuel condition. Rejetting in this case could solve the immediate
problem
(rich condition; poor performance), but could result in a lean
condition if you
cleaned the air filter and didn't rejet
back to where
it was (plus that's twice as much work as just cleaning the air filter
in the
first place). ANY mechanical/electrical problems need to be
addressed or
ruled out first before altering the jetting (air leaks, torn boots,
clogged
filters, shorts in the wiring, TORS system faults, bad grounds, water
in the
fuel, bad fuel, bad bearings, worn rings/pistons, etc.). This is
because
some mechanical and electrical faults can mimic or cause poor running
which
could otherwise be contributed to bad jetting. If you're certain
that the
jetting is the problem, the process would be:
1.determine if the condition is rich or lean
2.identify which carb circuit(s) is the
problem
3.correct the problem circuit(s)
4.verify that rejetting solved the problem
Q#7:What are some indications that my
jetting is
rich?
A#7:A slightly rich condition will result in
noticeably reduced performance, or "bog". Say your main jets
are one size too rich, it starts and runs fine, but whenever you have
the
throttle pinned (or Wide Open Throttle=WOT), the motor doesn't continue
building RPM; it bogs down because there's too much fuel per volume of
air and
it cannot burn efficiently. Other indications of being rich are
fouled
plugs, thicker than normal exhaust smoke when the motor is fully warmed
up, and
the dreaded overheating. Be careful of these symptoms though, as
any of
them alone may point to a non-jetting related problem (thick white
smoke is
more likely a head gasket leak, fouled plugs could be a weak
stator).
While overheating due to a rich condition is not common on Banshees
(typically
the plug will foul and not fire before it gets too hot), it's still not
a good
idea to run for extended periods with the jetting too rich.
Periodically
reading your spark plugs is a good way to get an idea of your overall
jetting; if
the center electrode (the part that's snow white when brand new) and
base ring
are light chocolate brown, you're jetting is perfect (slightly rich);
if it's
black and wet, you're too rich. Doing a plug
chop will
tell you for sure if your mains are too rich or lean (more on this
later).
Another trick is to warm up the motor, pop the choke out to the first
notch,
and ride it; if it bogs worse with the choke out you know you're too
rich. Some motor mods will cause a
rich
condition, as well as changes in temperature or elevation (see Q#13,
14, &
15).
Q#8:What are some indications that my
jetting is
lean?
A#8:A slighly
lean condition
can result in a hesitation, missfire, or
revving high
& fast with no power. Say your pilot circuit is lean, when
you start
it up with the choke "on" it's fine, but when you turn the choke off
it idles very high; there's more air per volume of fuel so it burns
hotter (in
this case airscrew adjustment may solve the problem). Other
indications
of being lean are a backfire and rapid overheating. Overheating
alone
will cause serious problems, so even a slighly
lean
condition is usually much worse than being too rich. Like rich
conditions, lean indications may not necessarily mean that jetting is
the
problem; an air leak between the carbs and
the
cylinder can exhibit the same symptoms as lean jetting, often if this
is the
case only one cylinder will act lean. Never take a lean condition
lightly, as it's the quickest way to damage your motor. Again,
spark plug
color is a good indication of overall jetting; if the center electrode
remains
white or light gray and the base ring shows not coloration after riding
for
more than half an hour (starting with fresh plugs-if the plugs were
already
brown for correct jetting they will not turn back to white if it's now
lean),
it's too lean. A plug chop will tell you for sure. The
choke trick
is an easy way to tell also; when the motor is warmed up, pop the choke
out to
the first notch, and ride it; if it runs better (no hesitation or
revving high
& fast with no power) then you know you're too lean. Most
motor mods that improve airflow will cause
a lean condition
(remember more air per volume of fuel=lean), and will require rejetting richer. Temp and elevation
changes can also
cause a lean condition (see Q#14 & 15).
Q#9:OK, I'm sure it's rich or lean, how
do I know
what to change?
A#9:For a breif recap of the Carb
Theory 101 link mentioned earlier; the carb
delivers
fuel depending on the throttle position:
0 to about 1/8 throttle is controlled by the Pilot jet size, and fine
tuned by
the airscrews
1/4 to 3/4 throttle is controlled by the needle taper & length,
fine tuned
by the clip position
3/4 to WOT is controlled by the main jet size
Once you know which circuit or circuits are rich or lean, you can begin
to dial
in the jetting.
Q#10:I have a bog or hesitation right off
idle, OR
an erratic idle, OR a very high or low idle...
A#10:Since the problem is between 0 and 1/8 throttle, the
pilot/airscrew
circuit may be rich or lean, and you may need to also adjust the idle
speed
screws and check the carb synchronization
(see Q#23
& 24). Start by adjusting the airscrews; on each carb
turn them in (clockwise; which is richer) a half turn (180 degrees);
adjust
both airscrews the same amount. If you have the motor idling
allow about
20 seconds for the motor to react to the new setting. If the
condition
gets worse, try going out (counterclockwise; which is leaner) on the
airscrews
and see if it improves. If going in on the airscrews helps but
the
problem persists after you turn the airscrews all the way in, or to
within a
half turn out from seated (don't torque the airscrews! the tip is
pointed
and overtightening them can cause
damage!), try the
next size larger pilot jet, and start over with the airscrews 1.5 turns
out;
tune the airscrews from there to get a clean idle and off-idle
response.
Conversely, if going out on the airscrews helps but the problem
persists after
you get to about 3 turns out from seated, try the next size smaller
pilot jet
and start over with the airscrews 1.5 turns out; tune the airscrews
from there
to get a clean idle and off-idle response. Once you acheive
a clean idle and crisp off-idle response (no bog or hesitation right
off idle),
you may need to adjust the idle speed up or down by adjusting the idle
screws. If airscrew adjustment does not have any affect on the
bog or
hesitation, and you are certain the problem is below about 1/4
throttle, check
the carb sync, make sure the pilots aren't
clogged
(it only takes a speck of dirt to block the tiny passage), and insure
that both
airscrews are set the same number of turns out from seated. Be
advised
that the stock Banshee carbs have a pilot
jet that is
specific to Banshees; a standard Mikuni pilot jet will not work (see
next
section for pilot jet details). To verify your pilot/airscrew
circuit
jetting, start the motor and let it warm up fully; install fresh spark
plugs,
start it (without using the choke) and let the motor idle for about 10
minutes;
pull the plugs and look at the center electrode and base ring; they
should be a
light chocolate brown color if you're dialed in. As a side note,
since
the pilot jets are flowing fuel throughout the throttle range (they are
solely
responsible for mixture at idle to about 1/8 throttle but continue to
deliver
fuel above 1/8 throttle) changes made to the pilot jet size MAY have an
affect
on the main jet jetting; if you change pilot jet sizes it's a good idea
to
verify your mains as well, and to a lesser extent the needle clip
position.
Q#11:I have a bog or hesitation at about
half
throttle...
A#11:Since the problem is between about 1/4 and 3/4 throttle, your
needle clip
position may be rich or lean. If you know the jetting in this
range is
too lean, move the needle clip down one clip position (richer-moving
the clip
towards the pointy end of the needle). If you're sure it's rich,
move the
clip up one clip position (leaner-moving the clip towards the blunt end
of the
needle). If you're not sure if you're rich or lean, try the choke
trick;
with the motor fully warmed up pop the choke out to the first notch and
see if
the problem gets better or worse; if better then try going a slot
richer on the
needles; if worse try going a slot leaner on the needles.
Remember to
check the carb sync whenever the tops are
off the carbs, and don't get the slides
reversed; the cutout on the
bottom of each slide should face the airbox.
Q#12:I have a bog at WOT, OR it revs high
&
fast with no power at WOT...
A#12:Since the problem is at WOT, your main jets may be rich or
lean.
Since the motor is spinning so fast (usually) when the throttle is
pinned, the
main jets are the most critical circuit on a Banshee; running too rich
or lean
on the mains can be extremely hazardous to your motor's health: rapid
overheating combined with high RPM's are a
recipe for
disaster. If you have done mods that
affect
airflow, start with the manufacturer's recommendations or those shown
below to
get a ballpark number on your main jet size. Similarly,
if the temperature or elevation has changed use the below guidelines to
get
your mains close (see Q#14 & Q#15). Once you think you
are
close to the right size on the mains, one method of dialing in the main
jets is
to start with large mains; if it bogs at WOT drop a size until it revs
out
clean; if it doesn't bog at WOT go up a size until it does and then
drop one
size. The bog at WOT is usually an indication that it's rich on
the
mains, however since running lean is usually worse than being a little
rich,
the choke trick can be used to make sure before you go leaner on the
mains:
with the motor warmed up pop the choke out to the first notch; if the
bog at
WOT gets worse you know you're rich and can safely drop a size on the
mains; if
it gets better with the choke out you're lean and should start going up
on the
mains until it bogs at WOT, then drop a size. Another method is
doing a
plug chop (see Q#33), but since you will be revving the motor out in
6th gear
it's best done to verify the mains after you have gone down one size
from
bogging at WOT as detailed above. When dialing in the mains it's
best to
err on the side of rich than lean to avoid any damage to your motor
(rich
symptoms are fairly obvious in the form of decreased performance, and
can be
remedied before engine failure-lean indications may not be apparent
until it's
too late). Don't be afraid to go big on the mains, as long as you
work
your way down to the point that the motor revs out clean all the way to
WOT
you'll be less inclined to risk damage from running lean.
Q#13:My jetting was perfect a couple
months ago and
now it won't run right; why?
A#13:If the outside air temperature has
changed by
more than 10 or 20 degrees Farenheit since
it was
jetted perfectly, you'll need to rejet to
compensate. If this is the case, typically you will need to rejet the mains a size smaller (if it was dialed
in for
colder weather) or a size larger (if it was dialed in for warmer
weather), and
possibly adjust the airscrews. If the temp has NOT changed, and
you have
not added any other mods or made any
changes that
could have affected the jetting, your problem could be as simple as
cleaning
the air filter to needing a fresh topend,
before you
alter the jetting rule out any other possibilities.
Q#14:Why do temperature changes affect my
jetting?
A#14:Since the carbs
deliver
fuel dependent on throttle position, they cannot compensate for changes
in air
density (only volume). As air gets colder, the molecules become
closer
together in a given volume (higher density); cold air contains more
oxygen than
the same volume of warm air. More oxygen in a volume of air means
that
the same jet sizes will not deliver enough fuel to burn the oxygen at
the
highest efficiency, and what results is a lean condition (just the same
as if
you decreased a jet size). On the flip side, as the air gets
warmer the
molecules are able to expand (lower density); so there's less oxygen in
the
same volume of air. Less oxygen in a volume of air means that the
same
jet sizes will deliver too much fuel, and the net result is that you'll
be
running rich. What that all translates to is that colder weather
will
require jetting larger (usually just the mains), and warmer weather
will
require jetting smaller. Going from colder weather to warmer
weather will
usually result in a bog at WOT (see Q#12), and when this happens you
can simply
go a size smaller on the mains (and possibly need to adjust the
airscrews, see
Q#10). Going from warmer weather to colder weather may or may not
give
you any indications that you're too lean (it may even run better; the
highest
performance is on the ragged edge of too lean, however this is also
where you
can risk damage from overheating rapidly). Mikuni says that a
main jet
size is good for approximately a 30 degree F temp range. While
true for a
stock machine, as you add mods the temp
range that a
main jet size works best for may be as little as 20 degrees F (for
example: 310
mains for 40-60 degrees F, 300 mains for 60-80 degrees F, etc.).
If
there's any doubt (especially if there are any indication of lean
jetting; see
Q#8), dial in the mains again (see Q#12) or do a plug chop.
Q#15:Why do elevation changes affect my
jetting?
A#15:In the same way air temperature changes
the
density of oxygen in a given air volume, so do elevation changes.
As the
elevation above sea level (0') increases, there is less oxygen per
volume of
air (lower density). Typically you'll need to rejet
your mains one size for every 1500'-2000' elevation difference; jet
smaller
when going to a higher elevation and jet larger for going to a lower
elevation
(for example: 300 mains at 3000', 320 mains for 0' or sea level IF the
temp is
the same). Bear in mind that you'll need to compensate for BOTH
temperature AND elevation changes, so going from a hot low elevation to
a cold
high elevation may net no jetting change. Much like temp changes,
going
from a low elevation to a higher one of the same temp will exhibit a
bog at WOT
because it's rich (dial in the mains-see Q#12); going from a high
elevation to
a lower one may or may not give you any symptoms of being lean before
damage
occurs. While there are other atmospheric factors that can affect
jetting
(like humidity, barometric pressure, etc.), temperature and elevation
changes
will have the most drastic affect.
Q#16:Why do premix ratio changes affect
my jetting?
A#16:Just like temperature and elevation
changes,
altering the amount of fuel delivered by the carbs
in
a given volume of air will result in a rich or lean condition. By
changing how much oil is in the premix, you also change how much fuel
is
available to burn. Since the oil in the premix is intended to
lubricate
the crank, it is burned off in the combustion process; however the oil
that's
in the oil/fuel mixture displaces the amount of fuel that is available
for the
air to burn; more oil means less fuel and less oil means more fuel,
from an
air/fuel ratio standpoint... For example, you change your premix
ratio
from 32:1 to 100:1, every gallon of fuel will contain less oil, so more
fuel;
from an air/fuel ratio standpoint there is more fuel to be burned so
your
jetting will be too rich and you'll need to jet leaner. In contrast, going from 40:1 to 20:1 means that every
gallon of
fuel will contain more oil, so less fuel; the air/fuel ratio will be
too lean
and you'll need to jet richer. Basically a higher ratio
will
require leaner jetting and a lower ratio will require richer
jetting. On
a side note, changing your fuel octane should not affect jetting.
Q#17:Why do some motor mods
require rejetting and others don't?
A#17:Whenever you alter the amount of air
flowing in
or out of your motor, you'll need to rejet
to
compensate. More air flowing in from a more efficient air filter
will
result in a leaner air/fuel ratio; more air flowing out from more
efficient
pipes will do the same thing; in both cases you'll need to rejet
to compensate (typically larger mains and sometimes larger pilots as
well,
depending on the mod). In addition, mods
that
affect how efficiently the air/fuel ratio can be burned will also
require rejetting (some ignition system mods
for example). Changes to compression ratio typically don't
require rejetting, however octane
requirements often will change
and are even more critical to preventing motor damage.
Q#18:Specifically what mods
will require rejetting?
A#18:Pipes & silencers, air filter(s), removing the airbox
snorkel, removing the airbox lid, reeds,
reed cages,
reed spacers, ignition advance, aftermarket coil(s), aftermarket CDI,
porting,
some aftermarket pistons that alter the port timing, altering the
premix ratio
(see Q#16), and obviously changing carbs.
Q#19:How much do I need to change my
jetting for a
mod?
A#19:It depends. With the multitude of
combinations of mods, along with the many
variables
from machine to machine and location to location, it's impossible to
know
anyone's exact jetting. However, it is possible to get close;
your first
resource is contacting the manufacturer (pipes, for example) or
machinist
(porting, for example) to get a rough idea or baseline for your
jetting; next
is to inquire about the jetting other people have for the same or
similar mods, if possible (keep in mind
that other mods, temp, and elevation
differences will be a factor);
post in the jetting forum at bansheehq.com; or use the rough estimates
in the
next section.
Q#20:I need to rejet
my
mains, how do I do it?
A#20:Start by making sure your Banshee is
clean,
specifically around the carbs. Turn
the petcock
"off" at the tank, and disconnect the fuel line at the first carb you're rejetting
(do one carb at a time so that the bowls
and/or slides don't get
reversed). Remove the choke hose, located between both carbs (just on the other side of the choke knob
on the left
carb). Disconnect the bowl overflow
line at the
bottom rear of the carb. Using a
small phillips-head screwdriver, loosen
the hose clamp on the
black rubber boot at the front & rear of the carb.
Push the body of the carb rearwards,
compressing the airbox boot, until the
front of the carb
clears the front reed cage boot, then twist the front of the carb outwards and pull the carb
free of the airbox boot. Stick a rag
on the top
of the motor right under the carb to catch
any fuel
that's in the float bowl. Using the same small phillips-head
screwdriver, remove the four screws that hold the float bowl on (don't
lose the
two little metal guides for the overflow hoses). Gently remove
the float
bowl straight off the carb body; if it
doesn't come
off easily tap the sides with the end of a screwdriver, just don't pry
on the
gasket mating surface or pull it off at an angle. Once off, check
the
bowl gasket, it will usually stay stuck to the carb
body but it doesn't hurt to check it for tears, or remove the gasket to
clean
it and the upper mating surface. After the bowl is removed, don't
rest
the carb on the motor, as you may bend the
floats
(the two roundish black plastic peices
that were inside the float bowl). Right in the center of the carb body (below and between the floats) you'll
see a
hex-shaped brass thing: that's the main jet. Sitting around the
main jet
is a white plastic splash sheild, slide it
off the
main and note how part of it goes into the carb
body;
that passage is where the pilot jet sits. Use a 6mm nut driver to
remove
the main jet, be careful not to lose the brass washer under it.
Now
install the new main jet with the old washer, being careful not to overtighten the main jet. Slide the shield
back over
the main and into the pilot jet passage. Put the float bowl back
on,
tighten the four screws, make sure there's no dirt in the carb
or boots, and put the carb back in the
boots just
opposite of how you took it out. Now do the other carb
the same way, replace the choke tube and connect the fuel and overflow
hoses,
turn on the fuel and make sure fuel doesn't flow straight out the
overflow
hoses. If it does, the float valve is stuck open, just tap on the
float
bowls with a large screwdriver and they should close.
Q#21:I need to rejet
my
pilots, how do I do it?
A#21:Follow the instructions above (A#20),
and find
the pilot jet instead of removing the main jet. Use a small
flathead
screwdriver to remove the pilot jet and install the new one. Make
sure
that the small pilot jet passage isn't clogged,
it
only takes a speck of dirt to block the pilot jet. Also make sure
you
have the pilot jets specific to Banshees, a standard Mikuni pilot jet
is longer
and will not fit (see below for more info).
Q#22:I need to adjust my needle clip
position OR
change my needles, how do I do it?
A#22:Start by making sure your Banshee is
clean,
specifically around the carb tops.
If you have
stock TORS carb caps, remove the side
retaining screw
and unscrew the carb top off the carb
body; if you have aftermarket Mikuni carb
caps,
simply unscrew them (do one carb at a time
if
possible to prevent reversing the carb
slides, if you
are unsure which slide goes into which carb,
look at
the bottom of the slide; the cutout or bevel at the base of the slide
should
face the airbox). Once the top is
loose, lift
it straight up and the carb slide below
the cap will
come out of the carb body. With one
hand, hold
the carb cap and bunch up the spring,
holding the
slide in the other hand. When you have the spring compressed,
look at the
top of the slide and notice how the gold-colored cable retainer
sits. Now
turn the slide upside down and the cable retainer will fall out.
You can
now push the cable from the carb cap into
the slide
slightly and move it to one side, freeing the cable from the
slide. Let
the spring decompress and leave the carb
cap resting
on the pipe or frame rail. Use a small phillips-head
screwdriver to remove the two screws on the top inside of the slide and
remove
the screws and retaining plate, then push the needle up and out of the
slide. To change the needle clip position, look at what clip
position it
is in, remove the e-clip with a pair of needlenose
pliers (you might want to do this part over a clean bench so you don't
lose the
clip), and then place the clip in the desired slot. Remember that
moving
the clip up towards the top or blunt end will make it sit lower in the
slide,
so the fuel flowing past the taper of the needle will decrease; so the
1/4 to
3/4 throttle jetting will be leaner. Conversely, moving the clip
down
towards the bottom or pointy end of the needle will make it sit higher
in the
slide, so fuel flowing past the taper of the needle will increase;
making the
jetting richer from ¼ to ¾ throttle. After setting
the clip position,
drop the needle into the slide, then drop the retainer in the
slide. Make
sure the hole in the top of the slide lines up with a notch on the
retainer,
this is to allow air to move in and out from the area above the slide
as it
moves, if not lined up you could have
problems with
the throttle sticking. Once the retainer screws are tight, bunch
up the
spring in one hand again, hang the slide on the throttle cable, and
drop the
gold cable retainer in place inside the slide. This is probably
the
hardest part, and a third hand here doesn’t
hurt. With the cable retainer in place, let the spring decompress
into
the slide. Now position the slide into the carb
body, making sure the cutout faces the airbox,
and
lower the cap and slide together into the carb.
Make sure the slide doesn’t hang on the
guide pin,
rotate the slide if necessary so the groove on the slide lines up with
the pin
inside the carb. You should feel no
resistance
as you drop the carb cap and slide into
place.
Also make sure the tip of the needle goes into the needle seat hole and
doesn’t hang up there. Carefully
thread the carb cap on the carb body, the
threads are very fine and the aluminum won’t
survive
cross-threading. Once tight, do the other carb
the same way. When both carbs are
done, be sure
to check the carb sync. Any time the
carb caps are off there’s
a
possibility that they won’t be tightened
to the exact
same location, so chances are the sync will be off.
Q#23:I need to adjust my idle speed, how
do I do
it?
A#23:If you have the stock TORS system, turn
the knobs
on the upper rear of each carb top equally
to adjust
the idle speed. If you have aftermarket Mikuni carb
caps and idle screws on the outside of each carb,
loosen the locknut on each idle screw and turn the screws equally in or
out,
then retighten the locknut. On a side note, if you installed the
idle
screws and they do not raise the idle speed when turned all the way in,
you
either need to file more material off the carb
body
where the locknut seats, or make sure the slides aren’t
reversed; on the left of the left carb
slide and the
right of the right carb slide is a small
ramp that
hits the tip of the idle screw, if the slides are reversed the idle
screw will
not raise the slides, and therefore change the idle speed (and it will
run like
crap if at all).
Q#24:I need to sync my carbs,
how do I do it?
A#24:There are several methods to tell which
carb to adjust; one is to use an airflow
meter at each carb, another is to use a
tool that measures vacuum
(Motion-Pro sells these for multiple-cylinder motors), and last is to
do it by
sight. Whichever method you use, the actual adjustment is the
same; for
stock TORS-equipped carbs, adjust the knob
on the
upper rear of the left carb top; for
aftermarket
Mikuni carb tops, loosen the locknut on
the left carb top and adjust the center
hex-shaped part that the
throttle cable goes into. If adjusting the left carb
will not sync the carbs, you may need to
set the
adjuster in the center of it’s range and
try
adjusting the right carb. To check
the carb sync by sight, remove the air
filter(s) and look into
the carb throats, watch the very bottom of
the carb slides as you gently push the
throttle. If one
slide moves before the other, you need to adjust the left carb
until they both move from zero throttle at
the same
instant. Once set, you should be able to pin the throttle and
release it,
and hear both carbs “click” shut in
unison; if you
hear two clicks they are still not in sync (or you possibly have a
problem with
either the slides sticking or the slide return spring).
Q#25:My throttle stuck wide open and I
almost
injured myself/my riding buddy/a small animal, what the hell?
A#25:Banshees are notorious for sticking throttles, 99% of the time it’s right after moisture hits the carbs;
hitting a water puddle, getting a little too happy with the pressure
washer, or
playing submarine. This may be one of the reasons Yamaha opted to
install
the TORS system, and so far a definitive solution hasn’t
been found. If water was indeed the culprit, start by checking
your carb top gaskets (see Q#22 & 24),
and make sure the
tops are secure (don’t forget to sync the carbs, Q#24, whenever you have the tops
off). Next
try using either silicone or waterproof grease on the throttle cable
where it
enters the carb tops. If water is
NOT the
problem, something is probably preventing one carb
slide to drop. Start by removing the air filter to see which carb slide is hung up. One possibility is
that a
piece of dirt from the fuel tank has lodged in the needle seat and won’t let the needle pass (see Q#27).
Another
possibility is that the guide pressed into the inside of one carb has backed out, allowing the slide to turn
and
hang. If this is the case, find the guide (located on the right
side of
the left carb body, left side of the right
carb body), make sure it is placed with the
tip vertical so
the groove on the carb slide will fit on
it, and use
a hammer & punch on the outside of the carb
body
to secure the guide.
Q#26:When I turn the fuel petcock “on”,
fuel dumps
out the overflow hoses, why?
A#26:Either you need to adjust the float
height, or
clean the float needle. If you’ve
just had the carbs apart or they have been
sitting dry for a while,
first see if the floats can be unstuck by tapping on the carb
bowls with a screwdriver handle. If that doesn’t
work you’ll need to remove the carb
and check the float height and float needle. Remove one carb top (see Q#22) and set the top assembly
aside, then
remove the carb body (see Q#20). Set
the carb body upside-down on a bench, then
remove the float bowl and gasket. Locate the pin that the floats
pivot
on, and use a small punch to drive the pin to one side (one end is
flattened
like a nail head so you can only drive it out one direction).
Remove the
pin and lift the floats straight up, hanging in the center of the metal
piece
connecting the plastic floats is the float needle. Slide the
float needle
off the float bracket, and look at the black rubber tip. If there
is a
speck of dirt on the tip of the float needle or the seat where the
float needle
sits, it will prevent the float needle from seating and let fuel
overfill the
bowl, and then run out the overflow hoses (if there is debris, see
Q#27).
If the tip of the float needle and the seat is clean, check the float
height. Hang the float needle back on the float bracket and set
the
assembly back in place so that the float needle drops into it’s
seat and the float bracket pivot holes line up with the holes in the carb body, then
reinstall the
pivot pin (tap the flattened end lightly to seat the pin). With the carb still sitting
upside-down
on the bench, measure the distance from the carb
body
gasket surface (WITHOUT the gasket in place) to the highest point on
the black
plastic floats (without putting any pressure on the floats).
This
measurement should be between 20mm and 22mm. If adjustment is
necessary,
gently bend the metal float bracket on each float to reach the right
height. A simple tool can be made to measure the float height out
of
cardboard, simply cut L-shaped pieces that measure 20mm, 21mm, and 22mm
from
the top of the L to the top of the leg of the L:
After setting the float height, reinstall the float bowl gasket, float bowl, and carb body. Install the carb slide and top, and if necessary do the other carb. Don’t forget to install the choke tube between carbs, check the carb sync, and if fuel runs out the overflow hoses when you turn the fuel petcock “on”, tap on the float bowls again to see if you can unstuck the floats.
Q#27:I removed my carbs
and found dirt/debris/filth in the float bowl, why?
A#27:If there’s
dirt in the carb bowls, chances are it got
there through the fuel
system and not through the air filter. This can lead to fuel
running out
the overflow hoses if dirt gets in the float needle (see Q#26) or
worse, a
sticking throttle (see Q#25). A common cause is that the
strainers inside
the fuel tank have fallen off the fuel petcock, allowing whatever
sediment
lurking in the bottom of your fuel tank to go straight into the carb. To check the strainers, turn the
fuel petcock
“off”, disconnect the fuel line where it Tees between both carbs,
direct the hose into a fuel jug, and turn the fuel petcock “on” until
the fuel
tank is dry. Remove the two large Phillips-head screws that
secure the
fuel petcock to the bottom of the fuel tank (depending on what pipes
you have
you may have to remove the front plastic and fuel tank to get to
it).
There should be two white plastic strainers attached to the fuel
petcock, if
one or both has fallen off get them out of the fuel tank and put them
back in
the petcock with a little super glue. If the strainers are
missing or
torn, either replace them or add an in-line fuel filter on the fuel
hose
between the fuel petcock and the Tee. The in-line fuel filter
will catch
anything that the strainers miss and should not have any affect on fuel
delivery (get a clear one so you can see when it gets stopped up and
you need
to replace it, having a spare in the toolbox is a good idea too).
Q#28:I removed my carbs
and found dirt/debris/filth on the slides or inside the boots, why?
A#28:The three most common causes of dirt
entering the
carbs are; the stock air filter not held on
by the airbox lid correctly, a torn air
filter, or a cracked airbox boot.
The stock air filter mounting system is
simply crappy, sure you can remove the air filter with no tools, but
how often
do you need to do that? And how many of us carry a spare clean
& oiled
air filter with us? Some people have no trouble getting the airbox lid on right so that it hold the air
filter (the
easiest way is to set the lid on one side and lower the other side in
place,
watching to make sure the lip on the lid catches tha
air filter cage), others never get it right (those are the guys that do
a topend after every ride). The best
solution is to
replace the entire air filter and/or mounting plate with an aftermarket
product
that will eliminate any possibility of the air filter not sealing
correctly. Pro Design and UMI Racing offer aluminum adapter
plates that
permanently mount to the front of the airbox,
and
allow a foam or K&N air filter to be securely clamped in
place. Toomey offers a 2 into 1
system that eliminates the entire airbox,
and single foam or K&N filters can be mounted
directly to the carbs. Anything is
an
improvement on the stock setup, just be sure to choose the right setup
for your
needs (opinions vary but in general you want to keep the airbox
and possibly the airbox lid if you ride in
wet or
muddy conditions, a foam filter for extremely dusty conditions, and
K&N(s)
with Outerwear(s) for sand). Whenever you clean your air filter
look for
any holes or seams coming apart that could allow dirt to pass and
replace or upgrade
the filter if necessary. Finally, if the air filter is OK make
sure there
are no cracks in the airbox boots.
Q#29:What is the TORS?
A#29:TORS is the Throttle OverRide
System found on stock Banshees. It consists of the large boxy carb tops, a switch on the thumb throttle
housing, a switch
on the parking brake perch, and a control box mounted to the frame rail
above
the left cylinder. The function of the TORS is to limit engine
RPM if the
parking brake is engaged, or if the throttle is released and the carb slides don’t
shut (see
Q#25). If the switch at the parking brake senses that the parking
brake
is engaged, it tells the carb tops not to
lift the carb slides. Similarly, if
the switch at the thumb
throttle senses that the thumb throttle has been released, the carb tops won’t
lift the carb slides. The problem
with the system is that
often the switch on the parking brake perch will fail to sense that the
parking
brake is not engaged, and will then limit RPM (the motor won’t
rev past idle); adjusting the switch is the first solution, eliminating
the
TORS is a better one. Other drawbacks to the TORS is that the carb tops are huge and makes jetting more time
consuming,
the entire system is one more thing that can (and usually will) fail,
and the system
adds unnecessary weight. Eliminating the TORS is well worth the
effort.
Q#30:How do I eliminate the TORS?
A#30:Several companies sell TORS elimination
kits (Toomey, Vito’s,
etc.) that
include aftermarket Mikuni carb tops,
throttle cable,
and an idle screw kit. The throttle cable and carb
tops are a simple matter of removing the old and installing the new (be
careful
with the carb top threads and remember to
check the carb sync, see Q#22). The
idle screw kit requires
removing the carbs, drilling a hole (on
the left side
of the left carb and on the right side of
the right carb), tapping the hole, filing
the casting flat, and
installing the screws. Drilling the hole is simple,
just place a small piece of wood inside the carb
to
prevent the tip of the drill bit from dinging the opposite side of the carb when it goes through. Tapping the
threads is
also easily done, however be careful to use a good quality tapping
fluid and
run the tap in slowly; half turn in, quarter turn out, etc.
Breaking the
tap off is an exceedingly bad idea. Make sure to file off enough
material
at the end of the casting, about ¼”, so that the idle screw can
raise the carb slide. Once
installed, you can remove control
box, the parking brake switch and thumb throttle switch (follow the
wires to a
connector and either disconnect it or cut the wires). Be sure to
clean
the carbs thoroughly and use compressed
air to blow
out any drill filings, and check the throttle cable free play.
More
details on installing the kit can be found at www.toomey.com in the
tech
section.
Q#31:What’s the choke tube and what does it do?
A#31:The choke tube is a small hose that
sits between
the two carbs, on the opposite side of the
choke knob
on the left carb to the left side of the
right carb. The tube allows fuel
drawn from the choke
circuit on the left carb to richen both carbs when the choke is “on”. If the choke
tube is
removed and the motor run, it will run like crap, if at all.
Q#32:What’s the choke trick?
A#32:The choke trick is an easy way to tell
if you are
rich or lean on one or more jetting circuit. Since the choke
richens the
mixture, you can use the choke to quickly find out if you need to
richen or
lean out your jetting: with the motor fully warmed up, pop the choke
out to the
first notch (half choke) and ride it; if it runs better with the choke
then you
know you need to go richer on your jetting; if worse you should be able
to
safely lean out your jetting. As with any other jetting issue,
make sure
you rule out any other possibilities before changing the jetting
(electrical,
mechanical, air filter, etc.).
Q#33:What’s a plug chop?
A#33:A plug chop is one way to verify your
main jet
jetting. To do a plug chop, make sure the air filter is clean,
warm up
the motor, shut it off and install two new spark plugs. Start the
motor
and pin the throttle, running through all 6 gears. When you wind
out the
top of 6th gear, hit the kill switch and pull in the clutch, keeping
the
throttle pinned. Remove the spark plugs (put in the old ones to
get home
if necessary) and put one in a vise. Using a
hacksaw,
cut the threads away from the center electrode with one cut parallel to
the
electrode and one cut perpendicular to the base of the electrode, so
you can
see the very base of the center electrode. If your main
jets are
spot on, you will see a 2mm tall chocolate-brown colored ring at the
base of
the electrode. If the ring is taller than
2mm or darker
than a Hershey bar, you’re rich on the
mains.
If the ring is smaller than 2mm or lighter, or nonexistent, you’re
lean on the mains. If both plugs aren’t
almost
identical, one cylinder may be richer or leaner than the other (if
leaner then
an air leak is likely on that cylinder). Keep in mind that doing
a plug
chop is best used as a way to verify your mains, since you will be
wound out in
6th gear there’s a potential for damage if
you are
way too rich or lean (see Q#12). While it’ll
cost you a couple bucks for new plugs, the plug chop, if done
correctly, I
believe is the single best way to find out if your mains are dialed in
for your
current mods, temperature, and elevation.
Q#34:What’s an air leak and why is it so bad?
A#34:An air leak is any place that air can
get into
your motor besides the right way: through the air filter, through the carbs, through the reed cage, and into the
cylinder.
An air leak can develop between the air filter and airbox,
between the airbox and airbox
boot, between the airbox boot and the carbs, at the carb
tops, between
the carbs and the reed cage, on the reed
cage boots
where the balance tube sits, at the reed cage gaskets, at the cylinder
base
gaskets, and at the crank seals. Anywhere that air can get in
will cause
problems, if it gets in before the carb
then there’s a potential for dirt to enter
the motor, causing
rapid ring wear and ultimately piston failure. Air getting in
between the
carb and cylinder or through a crank seal
will cause
a lean condition on that cylinder, which also will cause rapid damage
due to
overheating. Beware of any signs of being lean (see Q#8),
especially if
only on one cylinder, and immediately check for an air leak before it’s too late. To check for an air leak,
start the
motor and let it idle, then spray ether around the carb
boots, tops, reed cages, and cylinder bases; if the idle goes up you’ve found the leak. If the left
cylinder has an
air leak, it could be the crank seal (since the left crank seal is
between the
left crankcase and the flywheel, it seals air out), you need to perform
a
leak-down test to find out for sure. While the right crank seal
can also
cause an air leak, typically it will suck transmission oil and foul the
right
plug before it can drain the tranny and
start sucking
air. For information on doing a leak-down test see www.duncanracing.com
. As a side note, boost bottles sometimes cause cracks and
subsequently air leaks on the reed cage boots, the extra weight of the
boost
bottle vibrating may contribute to accelerated boot failure.
Q#35:OK, I need to rejet
my mains, pilots, and needles, what do I do first?
A#35:Starting with a rough idea of where you should be at on the jet
sizes and
needle clip position (either by the manufacturer’s
recommendations,
the advice of others with similar mods
taking temp
& elevation into account, or by the recommendations below), install
the
mains, pilots, needles at the recommended clip position, and set
airscrews 1.5
turns out. Make sure the air filter is clean and start the motor,
using
the choke if necessary, and let the motor warm up fully. Dial in
the
pilot/airscrew circuit first (see Q#10). Then dial in the main
jets (see
Q#12). Finally dial in the needle clip position (see Q#11).
Following this procedure will 1) make sure you aren’t
too lean or rich while warming it up (pilot/airscrew circuit), 2) make
sure you
aren’t too lean or rich at WOT, where it’s most critical, and 3) make sure you aren’t too lean or rich in the middle of the
throttle range
without confusing your main jet readings.
Q#36:Where the hell is the main jet/pilot
jet/needle/float etc. etc.??
A#36:Inside the carbs.
By the way, the carbs are those silver
things right
between the motor and the air filter. OK, OK, how’s
this:
Thanks to Meat for the pics!
For an exploded view of the carbs, take a
look at the
online microfiche available at www.yamahaoftroy.com.
Q#37:How do I read my spark plugs?
A#37:Aside from doing a plug chop (see Q#33), you can read your spark
plugs to
get an idea of your overall jetting (to see the base of the center
electrode
you'll still need to either cut the threads away or use an illuminated
magnifying glass). You’ll need to
ride for at
least 30 minutes to get a reading, but once done you can find out about
your
overall jetting, ignition timing, and spark plug heat range. Be
advised
that it’s not a good idea to ride around
when you
know it’s way too lean or rich (see Q#7
& 8 for
symptoms), and remember that unless the throttle is held at a constant
position
the jetting indications on the spark plug are an "overall" idea; one
circuit can be rich and can mask a lean circuit. Thanks to Boonman for the detailed instructions!
Refer to the illustration following instructions;
1. You set your heat range from the ground strap (this is the piece
closest to
the piston)
2. You do all the plug readings for jetting from the base ring (the
base ring
is what the ground strap is welded to at the end of the threads)
3. You determine detonation and timing issues from the porcelain (the
porcelain
shows preignition/detonation, it will not
accurately
determine jetting / air/fuel
ratios) DO NOT BASE JETTING DECISIONS ON THE PORCELAIN COLOR AT THE
TIP.
1. How to determining plug heat range:
The ground strap is your window to getting this right. If the "color"
of the ground strap "changes" too-close to the ground strap's end,
(the end opposite of the base ring), then the heat-range is
"too-cold" (heat transfer is too quick to the base ring). If
the "color" of the strap changes near where it is welded to the
base-ring, then it means that the plug heat-range is "too-hot" (heat
transfer to the base ring is to slow causing the deposits to be burned
off the
strap completely). The strap at this point could start working
like a
"glow-plug", probably resulting in pre-ignition and/or detonation.
The properly set heat-range is when the "color" is at the half-way
point on the strap.
2.
The base ring "color" is very close to the color of the piston crown
and is used to determine the jetting. You're looking for the soot color
to be a
nice light to medium brown, (color is always hard to describe) if the
color
doesn't go all the way around the base ring (at least one full thread
turn on
the plug) or the color is whitish it is way too lean. If the color goes
all the
way around, but there is a spotting of heavy dry soot on the top of the
color,
you are too rich.
3. Read the porcelain to determine detonation/preignition:
The first signs of detonation/preignition
will be
seen on the porcelain down in the plug, It
shows up as
tiny black or shiny specks of aluminum. Also look very close around the
center
electrode where the porcelain intersects, this will appear to be
melting
between the insulator and the electrode. Detonation is caused by the
air/fuel
mixture exploding rather then burning. This gives off a sound (a
knock),
this sound is the result of a shock wave, this
wave
disrupts the boundary layer of cooler gases that cover the internal
parts of
the combustion chamber. This causes a very rapid rise in pressure and
temperature. The results are holes in the top or sides of the pistons,
blown
head gaskets, broken rods (all bad stuff),
this can
also shock the rings from their seal causing oil to form as little
spots on the
porcelain.
Q#38:What’s the deal with the airbox
snorkel?
A#38:The black rubber snorkel on the front of the airbox
lid is intended to draw air a little higher than the airbox,
in an attempt to lessen the amount of water that enters the airbox
(and to a lesser extent, dust). However, the snorkel alone is
quite
restrictive. In most cases the snorkel can be removed without a
dramatic
increase in water intake, and will increase airflow enough to
necessitate going
one or two sizes larger on the mains (see Q#12). Keeping the
snorkel in
place after adding pipes will restrict airflow significantly, and you won’t see near as much hp gain with the snorkel
on (same
goes for the airbox lid, see Q#40). When doing mods such as
aftermarket pipes
and/or air filter, it’s best to remove the
snorkel to
allow your motor to breath efficiently. Removing the
snorkel and rejetting to compensate on a
completely stock machine will,
in most cases, improve performance slightly, while not risking any
damage
(unless you’re riding through water above
the seat,
and in that case you’re pretty much asking
for
trouble anyway).
Q#39:What’s the deal with the airbox
lid?
A#39:Like the snorkel, the airbox
lid protects the air filter from water & dust, and like the snorkel
the airbox lid can pose an airflow
restriction after a certain
number of mods (like pipes and air
filter).
Unlike removing the snorkel, removing the airbox
lid
on a completely stock machine won’t have
much affect
(even after rejetting to compensate), and
without the
lid in place to retain the stock air filter, the filter will fall off
allowing
dirt to enter and subsequently damage your motor. In addition,
running
without the airbox lid on, when using an
aftermarket
air filter setup that doesn’t require the
lid to
secure the air filter, can allow water and mud to enter the airbox.
If your riding conditions lean towards swampy, it may be a good idea to
keep
the airbox lid in place even after adding
pipes and
air filter, to keep the air filter from loading up and/or passing
water.
That said, if mud & water are not a concern, removing the airbox lid after adding an aftermarket air
filter &
adapter plate and pipes will allow the most airflow (short of a 2 into
1 or
dual filters), and still offer some protection from the elements.
Plus
you can keep the lid and throw it on when you wash your Banshee to
protect the
air filter.
Q#40:OK, I’ve
got my
jetting dialed in perfect for my mods and
elevation,
but the temperature ranges significantly during the day, what can I do?
A#40:EFI is the best solution, since it will
automatically compensate for changes in air density; this is still
prohibitively expensive though (at least in my opinion). Another
option
is a Dial-a-jet, which allows you to alter the jetting (by about one or
two
main jet sizes) with the turn of a dial (I don’t
have
firsthand experience so I can’t
comment). Aside
from rejetting the mains in the middle of
the day
(and possibly again in the evening), the only other alternative is to
use the airbox lid. Say you have an
aftermarket air filter
setup; dial in the mains with the airbox
lid on for
the coldest point in the day; then as the air temperature increases, it
will
start to run rich (bogging at WOT, see Q#12); simply remove the airbox lid (which is about equal to one jet size
on the
mains) and voila, you’re stylin’.
Depending on your specific mods, this may
or may not
work, but at least it’s an option (it
would be a good
idea to make sure you’re not lean when you
take off
the lid by reading the plugs, and don’t
forget to
replace the lid as the temperature drops, otherwise you run the risk of
being
lean).
Q#41:You said you’d
give
recommendations for different mods, what
are they?
A#41:First, realize that every Banshee is
different,
so these recommendations are only meant to get you in the ballpark for
your
jetting. Second, remember to add or subtract sizes for ANY of the
below
that apply (airbox lid, filter, temp,
elevation,
etc.). Third, if there’s any doubt
about jet
size, err on the side of rich to start with, and work your way leaner
(see
Q#12).
Assuming that your jetting is dialed in perfectly, add the following for each mod:
Air filter
Remove snorkel:1-2 sizes larger on the mains, adjust airscrews
Remove airbox lid:1-2 sizes larger on the
mains,
adjust airscrews
Add foam air filter:0-2 sizes larger on the mains, adjust airscrews
Add K&N air filter:4-6 sizes larger on the mains, adjust airscrews,
add one
size on pilots if necessary
Add 2 into 1 Foam air filter OR dual carb-mounted
foam filters (removing entire airbox, NOT
in addition
to removing snorkel and airbox lid
above):2-4 sizes
larger on mains, adjust airscrews, add one size on pilots if necessary
Add Dual K&N carb-mounted air filters
(no airbox, NOT in addition to removing
snorkel and airbox lid above):4-7 sizes
larger on the mains, adjust
airscrews, add one size on pilots if necessary
Add Outerwear:no change
Add TORS elimination kit:no change
Pipes
Add Pipes & silencers (all except 2 into 1 pipes):8 sizes larger on
the
mains, 2 sizes larger on the pilots, adjust airscrews
Note:Some pipes,
like CPI
and other “drag” pipes, may need even larger mains, midrange pipes may
only need
one size larger on the pilots
Add 2 into 1 Pipe & silencer:4-5 sizes larger on the mains, 0-1 sizes larger on the pilots, adjust airscrews
Reeds
Add Reeds, Aftermarket reed cage, or Ported reed cage:Move needle clip one position leaner,
adjust
airscrews, 0-2 sizes larger on the pilots
Electrical
Add Degree key or Timing plate with advanced ignition timing:0-1 sizes
larger
on the mains, adjust airscrews
Switch coil wires (A lot of Banshees come from the factory with the
orange
positive wire on the “-“ terminal of the coil, and the black ground
wire on the
“+” terminal of the coil, switching the wires would put orange on “+”
and black
on “-“):0-1 sizes larger on the mains, adjust airscrews
Add Aftermarket ignition system:4-8 sizes larger on the mains, adjust
airscrews
Compression
Add Coolhead with smaller domes or shave
stock head:no
change
(be advised that your octane requirements may change)
Miscellaneous
Overbore:no
change
Re-ring pistons:no change
Forged pistons (stock crown, port timing and pin location):no change
Weld crank/rebuild crank:no change
Lighten flywheel:no change
Rewind stator:no change
Boost bottle/aftermarket intake manifold:no
change
Clutch/transmission:no change
Elevation
For every 1500-2000’ above sea level, add to above:1 size smaller on
the mains,
adjust airscrews
For every 1500-2000’ change in elevation after jetting is dialed in:1
size
smaller on mains for higher elevation, 1 size smaller on mains for
lower
elevation, adjust airscrews
Temperature
For 60-90 degrees F:no
change to above
For every 20-30 degrees F colder than 60:1 size larger on the mains,
adjust
airscrews
For every 20-30 degrees F warmer than 90:1 size smaller on the mains,
adjust
airscrews
For every 20-30 degrees F temp change after jetting is dialed in:1 size
larger
on mains for colder temp, 1 size smaller on mains for warmer temp,
adjust
airscrews
Humidity
Very low humidity to very high humidity:0-2
sizes
smaller on mains, adjust airscrews
Very high humidity to very low humidity:0-2 sizes larger on mains,
adjust
airscrews
Premix Ratio
32:1 ratio:no
change to
above
Higher ratio (40:1, 50:1, etc.):0-2 sizes smaller on mains, adjust
airscrews
Lower ratio (20:1, 24:1, etc.):0-2 sizes larger on mains, adjust
airscrews
Example
Your Banshee is bone stock, 32:1 premix, you’re
at
sea level and it’s 60-80 degrees.
You add a
K&N air filter, remove the airbox
snorkel, remove
the airbox lid, and mount Pro Circuit
pipes &
silencers. IF your current jetting is 25 pilot, 200 mains, start
by going
up to 340 main jets (14 sizes larger; 8 for pipes, 4 for K&N, 1 for
snorkel, 1 for airbox lid), 30 pilots (2
sizes larger
for the pipes), leave the needle clip in the stock location, and start
with the
airscrews 1.5 turns out. If you got some reeds at the same time,
everything would be the same except you’d
start with
the needle one clip position leaner than stock.
Q#42:You don’t
have
recommendations for porting in the mods
above, why
not?
A#42:Porting is always the wildcard as far
as jetting
is concerned. With so many different variables there’s
no way to even come close. Suffice it to say, always start on the
rich
side and work your way down (see Q#12), this goes for pistons that
alter the
port timing as well. However, a reputable porting shop should be
able to
get you real close on your jetting, if they can’t,
don’t give them your cylinders…
Q#43:I followed all your directions above and now my Banshee won’t run, my wife left me, my dog bit my leg, a
giant
asteroid is on a collision course for earth, blah blah
blah…
A#43:So you want a disclaimer? Allright:
the
thoughts and opinions expressed on this page are solely those of the
author,
who takes no responsibility whatsoever for the results of any actions
that may
injure or kill the planet’s inhabitants if
done at
home or in the parking lot of a 7-11, and who by the way is NOT laying
on a beach
in the Carribean sipping exotic elixirs
and tapping
the asses of scantily clad beach bimbos right now because he didn’t make a damn cent off of trying to help
fellow
enthusiasts by composing this document. If you want to piss and
moan,
file litigation, protest in front of the White House, whatever…tough
shit, I’m goin’
riding.
One more big thanks to all the awesome members of the www.bansheehq.com forums for all
your help
and input, I can't name you all but you know who you are, I couldn't
have done
it without you!!
This document is Copyright © Ben Boal
2003. Any unauthorized reproduction or sale of this document is
unlawful and violators will prosecuted to the full extent of the
law. In other words, don't sell it. Print it out and keep
it for future reference, give it to your friends, link directly to this
page, whatever, but it's intended for informational use and reference
by people who would rather ride and have a good time than turn a quick
buck on someone else's efforts. You know who you are, dumbfucks
trying to sell what is free...someday you're gonna run into me in a
dark alley and wish you weren't such a puss.