81 750e idle probs when warm

[Guest]

Hi all, my gs750e starts fine & runs good for about 5mi, then dies completely when the throttle is closed. It acts like it is starving for fuel. It won't restart for about 5min. Tried running it on prime w/same result. Good fuel flow to carbs on prime. Cleaned carbs, has good fuel flow to carbs when engine turns over with petcock on reserve or main setting. Has good spark when hot. Any ideas? I'm stumped. Thanks in advance for any feedback.

[tom203]

Did this problem come on suddenly? Make sure tank cap is venting (so fuel can flow to carbs). Check that idle stop screw/bracket has not loosened up.

[MAdams450]

I tried running with fuel cap loose. Idle bracket is fine. Really seems like fuel flow prob since it starts back up after 5min.

[jwhelan65]

Did you clean the carbs?

[MAdams450]

Yes, twice.

[MAdams450]

Going to pull the petcock and check that again. Carbs are definitely clean. New o rings in all carbs. Float height looks good. I don't have a synchronizer for the carbs, but don't think that's an issue since it runs good for a while.

[tom203]

It does sound like fuel delivery problem, but if petcock is flowing fuel OK, then it's internal to carbs. Next time it dies -with petcock in "on" or "res" spot-, can you check for fuel in one bowl ?

If you kept running (didn't have to close throttle) would it still die? or is it when you drop to idle?

[MAdams450]

It starts to bog pretty bad while on the gas. Last time it died, I quickly pulled the #4 drain screw and gas came out, but I don't know if it was a full float bowls worth.

[MAdams450]

Another interesting note-when the engine was about to die, I pulled the choke out and it almost started to run again. Thinking that extra bit of gas gave it a couple of extra seconds of run time before it starved out.

[tom203]

A good flowing petcock on PR would refill semi empty fuel bowls quicker than 5 min- definitely recheck petcock flow. You got spark when this problem arises, so it's got to be fuel related. The fuel enricher (aka "choke") draws from very bottom of fuel bowl,so yeah it might give it a slight burst even if bowl fuel level was real low.