Jetting Suggestions

[thr3shold]

I've got a 1980 gs1100e it has a 4 into one with a supertrapp , pod filters, and 33 smoothbores. The pilot air screw (?) is turned almost all of the way in so I'm pretty sure I need to get different needles and such (I've had the bike for a while, but have never tuned it properly). With the set up I have now, what sizes should I start at?

[RacingJake]

Does it idie fine and run smooth up to redline. Have you done a plug chop to see if the plugs are a tan color. Can't help you out with the 33's pilot screws.. don't know if its an air or fuel adjustment??

[gsbill]

I've got a 1980 gs1100e it has a 4 into one with a supertrapp , pod filters, and 33 smoothbores. The pilot air screw (?) is turned almost all of the way in so I'm pretty sure I need to get different needles and such (I've had the bike for a while, but have never tuned it properly). With the set up I have now, what sizes should I start at?

You may just need bigger pilot jets and pick the neddle up a notch or bigger main jets.

[thr3shold]

The way it is now it responds well in the low RPMs, but once I get in to the high range it bogs down. The plugs are sooty. Is there an online explanation of the different circuits within this carburetor? So I know what changing a jet or needle or what have you will do?

[thr3shold]

I found the mikuni tuning pdf file that first timer put up. Thanks dude.

[KEITH KRAUSE]

The way it is now it responds well in the low RPMs, but once I get in to the high range it bogs down. The plugs are sooty. Is there an online explanation of the different circuits within this carburetor? So I know what changing a jet or needle or what have you will do?

Very simple. It's all about throttle position when reading plugs/performance.
Full throttle to see what the main jet is doing.
1/3 throttle to see what the jet needle is doing.
Minimal throttle/idle to see what the pilot circuit is doing.
The hardest part is where you have overlap effect between two jetting circuits, especially from idle to about 1/5 throttle. You have the pilot circuit transitioning to the cut-away transitioning to the jet needle. Happens quickly and can be difficult to jet well. Accurate reads at or near idle are hard to judge too. Very inconsistent sometimes, especially if you don't do a good carb vacuum synch.
If you have dark plugs and bogging at the "high range" as you describe, sounds like you need to lower the jet needles by raising the e-clips. But it depends on actual throttle position where you're having these problems. The mains may be too large and you're really trying to describe only full throttle? Could be both the needle positions and mains too. Test at each throttle position first.