Carb Fact Sheet (by Larry aka Half_Crazy)
The straight skinny on carbs.
Let's start at the beginning of the air path.
After much experimentation, you can't beat the stock airbox
and open top K&N air filter. It's as good as it gets on one of these
bikes. Most owners of other motorcycle brands WISH they had an airbox
this well engineered. That's a fact.
Moving on to the carbs: These things are so
absolutely simple. It's an air passage and has 3 fuel passages. There
are jets that meter how much fuel is flowing into the air stream as air
NEEDLEJETS: Just a funny shaped block of metal with a hole through
the center. That's it. No one needlejet is better than another. Factory
Pro says their needlejets are patented "high dispersion"... Funny, I
have replaced like 50 of those things and they look just like the OEM or
the replacements I made. Just a tube.
If you are fortunate enough to have the stock, OEM, Factory
Suzuki/Mikuni needlejets... KEEP THEM! NO replacement is any better.
They will last FOREVER.
No one's replacement needlejets work any better than anyone else's in metering fuel. To say that this one or that one delivers better mileage or performance is total bullshit. The question then becomes how long will they last? The BEST needlejets are the ones that came in the bike. That's a fact.
Jetting/Tuning: There are many ways to skin a buck.
What you are looking for is the best compromise of all three fuel
circuits to get the most seamless and strong delivery of power to the
ground. You see people say to use:
Now for the kicker: Changing your mix screws by 1/4 turn (37.5's)
will make your main jets off by a size. That's right, the pilot circuit
feeds fuel at full throttle too.
Many times people will write to me and say, "My stage 3 runs great. It pulls like crazy, is smooth, never a hiccup, and gets 40 MPG consistantly... but when idling I get a little 'poof' out the pipes every 6 to 8 seconds. How can I get rid of this?".
My answer would be not to compromise the way it runs over an occasional 'poof'. Call it character. How much time do you spend idling?
I designed my jetting packages (G-Man sells them now) to be the best
compromise for all riders, work with many exhaust systems, be easy to
tune, easy to install, and return decent fuel mileage. I designed my
replacement needlejets to be as close as possible to an exact diplicate
of what came in the bike when new. Much much research and R&D went into
these. They were tested many many miles on several volunteer's bikes and
re-done through several generations using different materials, different
platings, different bore sizes, etc. before being sold to anyone. Once
for sale, the buyer could rest easy that if there was ever an issue I
would make it right at no cost to them. I eventually replaced most of
the early generation parts with later designs (for free) which I didn't
mind at all. I had ONE customer that was unhappy with what I did. I gave
him a FULL refund, inculding shipping, even though I knew he was unhappy
because his bike had other issues. I was the one who had to sleep at
night. My guarantee let me sleep well, knowing I had taken the high road.