82 GS750T won't stay running at low rpm

[denouden]

My bike has had the carbs cleaned and synced. There was one jet (not the main, the one just above it covered with the rubber plug) in one carb that was stripped when I got to it so I was unable to get it out and clean it.

When I put it back on the bike, it ran great for a few hundred miles and then began to stumble and hesitate upon acceleration...then you could hear the bike just all the sudden fire on all four and take off like normal. The sudden "firing on all four" would happen at whatever rpm it felt like at that time. It usually helped if I held the throttle at speed, listen for the exhaust sound change (like it was firing on 4) and then give 'er.

I had a shop look at it and he took the carbs apart and cleaned them again, paying special attention to above stripped jet. We were both a little weary of trying a reverse drill bit to try and get it out as that may turn into a very costly thing if all doesn't go well.

Anyhow, put them back on the bike, ran great for another few hundred miles and now it stumbles at idle. Anything above 2500/3000 rpm, it's goes like normal, anything below and it spits and sputters and tries to die out.

The tank is clean...there is no rust or any sediment in it, both I and aforementioned mechanic checked.

We were starting to think it may be ignition related (coils etc.) We replaced the plugs and wires and it ran better but still stumbles.

What do you guys think? Should I try the coils, or should I try drilling that jet out and risk a 400 dollar repair bill if it gets more screwed up. Is there a better way to try and get the jet out? Would a machine shop have better luck trying it - or other kind of specialized shop?

Anything else that comes to mind would be great. It runs great, just not at low rpm's...

Thanks.

[isaac]

If you've already gone through the carbs twice, there's no way that one idle jet would cause all that trouble. If the ignition was weak and allowed the plugs to foul, it'd do this. Weak spark can come from coils with too much resistance at the primary terminals. Those should be the orange/white and the white wire on one, and the orange/white and black/yellow on the other. Check resistance between those. If it's above 5 ohms, replace the coils. Check the resistance between each coil's plugwires at the connectors. If it's about 31k ohms, you're good. If it's drastically below that (my blown one showed 800 ohms) then replace the coil.

[KEITH KRAUSE]

The stripped pilot jet would not cause your problem. You said the bike ran fine for a few hundred miles which is further proof. If the stripped pilot jet was blocked in some way, you could have problems, but not the way you describe.
Did you put the rubber plugs back over the pilot jets?
Are the mixture screws set at their correct settings? Did you move them?
What rpm does the bike idle at when warmed up?
Do the rpm's rise significantly higher as the bike warms up?
Did you see the carb synch done?
Have you taken the plugs out to check their color?

[denouden]

-The rubber plugs were in good shape and put back on.
-As far as I know, the carbs were synced and mixture screws were adjusted properly. I bought the bike from a guy who played around with alot of things - not knowing what he was doing....so they were all set too lean and so they were adjusted.
-The bike doesn't idle at anything below 2750 or so, anything lower and it stumbles and dies. Although, when I pull up to a light and pull in the clutch, it'll run fine for a couple seconds and then start to do it's stumbling thing.
-Yes, the plugs were fouled after only a few hundred miles but I assumed this was because of the carbs being so out of whack before being synced & adjusted. They were then replaced again.

From what you guys are saying...I should try the coils before messing with the carbs any furthur? The plugs and wires were replaced, so the coils would be the only thing left to check correct? (ignition wise). The bike did definately see an improvement when those were replaced...so maybe is will be the coils fault after all...

[denouden]

It was one of the orange.white leads to the coil for 1&4. It was hanging on by a couple strands...redid it and she runs like a top.

Thanks....

[KEITH KRAUSE]

It was one of the orange.white leads to the coil for 1&4. It was hanging on by a couple strands...redid it and she runs like a top.

Thanks....

Glad to hear it! Too much resistance after the heat built up.