problem starting when hot

[rem3160]

I have a 1981 gs550l that will not start when hot I have checked the electrical system all o.k. I reshimed all the valves to spec. did compression check all cyl. 135 to 140. It starts right off when cold but when I ride it and get it warmed up it will not start it rolls over very well and i'm at a loss now what do I start looking for next starting to get frustrated.

 

[Reddog170]

Might be the petcock. If the vacuum line hookup is leaking it may be flooding it when it is warmed up.

 

[rem3160]

My plugs are all dry I checked them today when it was still hot.

 

[Nessism]

Is the bike stock or modified? Have you gone though the carbs and replaced the O-rings, including the intake boot O-rings? Vacuum synced the carbs? You giving the bike a little throttle to start when warm?

 

[xxBenJamminxx]

Do you have good voltage at the coils? On my 550 I had a hard time hot starting and after cleaning all electrical connections, grounds, and then doing the coil relay mod I haven't had a problem since.

 

[Guest]

Sometimes the coils can be known to fail when they get hot but it's a bit of a rare thing. More likely it's connections of some sort. Good advice to go through all your connections and grounds. Was the bike running fine before? A friend had that problem turned out to be a bad ground connection. Another possibility is starter bushings.

 

[rem3160]

This bike is completely stock I bought it new in 81 and have kept up and maintained everything all through the years along with my local dealer who retired and closed. Now I guess i'll go through all the connections and grounds to make sure there all right and check the coils.

 

[tom203]

Next time it fails to "hot" start, check for spark at plugs (when still hot)- maybe your ignitor is not cooperating when it gets warm. Does it actually cut out while you're riding or just refuses to hot start after shutdown?

 

[rem3160]

nope runs fine while running just won't start when hot.

 

[UK-GT]

Have you got some spare spark plugs that you can take with you, that way if it does not start whip the leads off, connect the spare plugs up and see if they are sparking!!
My 4T pit bike never wanted to start when it was hot, I had to open and close the throttle a few times and then try and start it, that normally worked, I suspected the heat from the head evaporated some of the fuel in the carb as the carb was hot to touch.
If you turn the engine off when it is hot and the try and start it straight away does it start? or will it not start if it has been left for a few mins?

 

[rem3160]

Update I run all the electrical tests on coils and igniter and all tested o.k. I started running a treatment for this ethanol fuel and now it will start when hot by giving it just a little gas so now i'm going to take the carbs of and give them a good cleaning and see what that doe's.