82 GS750 Won't run after engine is warmed up

[82Suzie]

Won't run after engine is warmed up

Yesterday I took my 82 GS750 out for a ride, it performed great, the engine was powerful and smooth.
But later in the evening after the engine cooled down I tried to start it and it only ran while the choke
was on. Today I tried again and it won't idle, only runs with full choke and after the engine warms up it won't run at all.
It has never acted like this before, I'm stumped.

Any ideas??

[KiwiAlfa156]

The choke on Mikunis is actually a separate mini-carburetor integral and in parallel with the main carburetor body. It draws fuel from the float bowl and air from the bellmouth, but shares nothing else with the warm running carb fuel or air circuits If it runs on the choke but won't with the choke closed, means it's unlikely to be ignition/timing -at least when it's cold. Check for a spark when warm to make confirm it's not ignition.

Will it run with the choke partially on when warm and die when you close the choke? If it does my suspicion would be a blockage in the idle/pilot circuits of one or more of the carbs. Does it just drop dead or is stumbling before it stops running. If it stumbles and it's a it's possibly one or two carbs blocked. If it dies possible that it's sediment could have blocked all the carbs if none of them is fueling.

Post a video if you can.

[ajh]

possibly a bad air leak from the manifolds that will get worse as rubber warms up?

If it doesnt run at all though I'd be thinking about major things that effect all cylinders as I'd expect it to run on 2 albeit badly. Maybe check to see if you have enough gas flowing into the float bowls, (I had problems with starvation because of an elongated fuel hose)

[Gorminrider]

not to be a nag, but if you browse the other threads, you might find some specific solutions to narrow your troubleshooting.

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[82Suzie]

Done, sorry for misplacing my question.

[Gorminrider]

Like every one above, it Definitely sounds like the carbs and if it won't run on three cylinders either, fuel supply seems suspect..kinked hose, dirty tank filter, petcock not opening, vaccum line to petcock iffy...stuff like that.

[gustovh]

Plugged gas cap vent is a possibility, but my money is on dirty carbs.

V

[82Suzie]

So far I've learned the Petcock is flowing gas, but as I said before the engine will no run after it warms up. Cold it will run with chock on, but once heated up it will not. Darnest thing.

[Forden]

Fuel starvation does seem likely, but I would also check ignition when warm as KiwiAlpha suggests. I've had outboard coils act up only when they got hot--if you run with the tank off, maybe check them for overheating then test them with an ohm meter.

[82Suzie]

Problem solved.
It was a fuel starvation issue caused by a leaky vacuum line from Petcock.
Tip of hose was hard and leaked, simply clipped a 1/4 i nch off the tube and reinstalled.
Suzie purrs like a kitten now.