1975 GL1000 starting issue

[Yellowjacket]

I have an issue with my bike starting on occasion. When it does start it runs great. It is not a battery issue or charging issue plenty of charge. What happens is this. Today after it sat for a couple days it fired right up. Rode it for about 15 minutes till it was fully warm. Stopped it and started right up. Then I let it set for about an hour and it would not start up. The way I can get it to start is to shut off the petcock valve, continue to try and start it, then when it is starved for fuel it will fire up and run fine. Any thoughts or suggestions will be helpful. I am here in Billings Montana were riding season is short.
Thanks

[ericheath]

Your description sounds like fuel leak into the carbs. Try ALWAYS turning your petcock off, which you should do anyways. This might help temporarily but is masking an issue that will likely get worse. Failure to turn off the petcock can result in a bent rod—— I have proof.

Three leak areas:
1. Plenum gasket
2. Carburetors to plenum seal (oring)
3. Leaky or sticking float valves

1-2 can result with fuel in the plenum floor (wet floor easily seen through air box.

3 is probably more common. Remove slide caps to see it coming through the jets in the carb throat.

[Yellowjacket]

Thanks. That is what I thought. No Fuel in the plenum I checked that yesterday. I will pull and check the float valves.

[redglbx]

Curt, a quick check is to pull all the plugs out and crank it over to see if the cylinders are flooded, it will shoot a stream if it is. I have seen one shoot over 20ft so protect yourself and make sure nothing you don’t want gas on is in the way.

If you have a wet cylinder you probably have a bad float/float valve, and that will tell you which cylinder is the problem.

[gltriker]

Curt, a quick check is to pull all the plugs out and crank it over to see if the cylinders are flooded, it will shoot a stream if it is. I have seen one shoot over 20ft so protect yourself and make sure nothing you don’t want gas on is in the way.

If you have a wet cylinder you probably have a bad float/float valve, and that will tell you which cylinder is the problem.

Make 100% Sure the Off/Run/Off handlebar switch is turned to one of the two Off positions, FIRST!

Flamethrower

[Sidecar Bob]

A few years ago the GL1000 engine that was in my bike had the issue everyone is pointing to but I don't think that is your problem. Mine would always start after sitting but would either struggle or be unable to start if it sat for less than about 10 minutes. When the starter motor couldn't turn the engine I could always start it by rolling down a small incline so I blamed the starter motor and chased that for a couple of years (including 2 rebuilds, a replacement and a replacement for the replacement).
I can't remember why but I had the carbs out for something else and connected them to a hanging tank and noticed that fuel pooling on the bottom of the plenum was running through the carbs and out of the manifolds (on the bike this would partially fill one or more cylinders). Further investigation revealed that the carb to plenum seals had failed and replacing them completely cured the problem.

BUT as I said, I do not believe this is your problem because 1) when it happened the starter motor could not re-start the engine until it sat for a while (I believe this allowed the fuel in the cylinders to evaporate) and 2) you don't have fuel in the plenum.

It is possible that one or more float level is too high and allowing the associated cylinder(s) to flood (removing the plugs and cranking the starter as described above will tell you that)(And as Gord said, make sure the kill switch is set to OFF)
But if the starter motor is turning the engine over easily I would be looking at things like whether the chokes are opening & closing properly.
And speaking of that, if it is cranking easily have you tried with & without choke?