carb equalization

[Anonymous]

I have an 82 GS1100, over the winter I installed a vance and hines 4 into one pipe, rebuilt the carbs and installed a stage two dyno jet kit. the bike idles almost flawlessly, has good throttle response and top end horsepower seems to be very good. the carbs have been balanced, the only thing that concerns me is that on moderate to hard acceleration I can feel a slight vibration and #2 pipe seems to be blueing faster than the others. It has a new fuel cock and there are no air leaks. I pulled and changed the plugs last weekend, they all looked to have good color. the valves are all adjusted within 1 mm of each other. My question is should I raise the needle on #2 carb or just put my helmet back on and get over it?

[KEITH KRAUSE]

I would not raise the needle. If the same needle setting works fine for the other 3 carbs, then something else is causing a lean mixture in that carb or cylinder. The blue pipe says that cylinder is running hotter than the others but you can't be too far off if your plug color is good. The plug color is telling you it's running good at most throttle positions, but at a certain throttle setting you're running lean. This would make me think the carb synch needs to be re-checked and the vacuum level set just a bit higher in that carb, as long as its level does'nt go more than a cm above the others. This would "richen" it up a bit.
Since the carbs were taken apart, it could also be the mixture screw was not set back to its exact setting. If you took it out, did you just put it back in the same amount as the others, or did you actually count the # of turns for each carb? These screws are commonly set at different points because of differences in each cylinder. If you're not sure, an additional 1/2 turn out will richen it a little.
It could also be a low float level. Did you set them?
Those are the 3 things I would check first, because you did say the carbs are clean and rebuilt inside and the valves, etc, are correctly set.

[Anonymous]

Thanks for the feedback, I think thats what i'll do, go back to square one and recheck. when I rebuilt the carbs the kits came with all new needles and O-rings and such, but all the mixture screws are set at the one and a half ( I think ) turns that dynojet recomends.
Thanks again,
Kent

[Anonymous]

Thanks for the feedback, I think thats what i'll do, go back to square one and recheck. when I rebuilt the carbs the kits came with all new mixture screws and O-rings and such, but all the mixture screws are set at the one and a half ( I think ) turns that dynojet recomends.
Thanks again,
Kent

[KEITH KRAUSE]

I have experience with Dynojet kits and I can tell you their "base settings" for different areas of jetting are sometimes way off. Still, you only have 1 carb that's not quite right, if it is the carb.
Also, I just noticed from your first post, you said the valves are all adjusted within 1 mm of each other. If this figure is correct, your valve clearances need re-checking. The clearances on my '79 GS1000E are to be within .03-.08mm. If you meant .01 mm then you're fine as long as you're within your models spec's.

[Anonymous]

What about an intake o-ring leak as causing the lean condition?

[KEITH KRAUSE]

What about an intake o-ring leak as causing the lean condition?

That's possible. But in his first post he says there are no air leaks, so I take his word for it.