Carb problems

[Anonymous]

Ok so the setup is 79 gs1000 bored to 1100 (wiseco) with Andrews 390 lift cams, old skool yoshimura pipe, stock 26mm carbs with Dynojet stage 3 kit and pod filters. Bike runs great in midrange and wide open but the idle sucks. When cold the bike idles relatively well but once its good and warm the idle will creep up to 1500-2000 then drop down to 1000. also the idle is slow to return below 2000 if throttle is wicked. I've cleaned the carbs thoroughly ,twice, set the fuel screw to 1 turn and the air screw to about 1 turn . Any one have advice, suggestions or a match? 8O

 

[lhanscom]

It's possible you may still be a bit lean on the idle screws, but with the cams you've got, idle is not where the want to be. That may be your problem.

 

[RacingJake]

Since it's a 1100 now I'd install some bigger carbs, 26mm sound alittle small. Or try bigger pilot jets :?:

 

[Anonymous]

Right now its a cost issue, I will be throwing on bigger carbs in the future but don't have the $$ now so I'm trying to get by for a bit.

 

[KEITH KRAUSE]

meanman, I have a '79 GS1000 with similar mod's. Your high idle rpm when warmed up is probably bad o-ring(s) in the rubber manifolds. If you replace them, put a good coat of hi-temp' bearing grease on them and torque to 6 ft/lbs by replacing the phillips screws with allens. Also check the manifold clamps for tight and that the carbs "popped in" correctly. Check the manifolds too for cracking.
Your pilot screws (underneath) and your side air screws are not set right.
The pilot screws commonly come from the factory set at different points to allow for small differences in each cylinder. To get them close, you sometimes have to do a lot of tinkering and take plug reads. When you seat them, do it LIGHTLY to avoid breaking the sharp tip off in the carb body. With your mod's, try 1 1/2 to 1 3/4 turns out for starters. Like I said, to get them exact, you'll probably find that they end up at different points. There may be a difference of a 1/2 turn between the "richest" and "leanest" screw. Don't turn them out beyond about 2 1/2 turns. If you don't get the results you want by this point, you'll have to try a step up on the pilot jets (17.5?) and re-adjust the pilot screws.
The side air screws should always be set to achieve the highest idle at normal operating temp'. Make sure the pilot screw adjustments were made, then put the bike on the centerstand and warm it up first. Turn the side air screws "two at a time" in 1/2 turn increments to more easily hear the rpm's rise and level out. Fine tune all four screws until the idle is at its highest. Now adjust the idle to about 1,100 rpm by using the idle screwknob. If your carbs are working well, these air screws will end up about 1 3/4 to 2 turns out.
The stock VM carbs really require a good vacuum synch. The mercury levels should be within 1 cm of each other at about 3,500 rpm. Any larger difference will result in uneven mixtures. Let me know how it goes.