Idles good, not good at highway speeds

[chowell]

I've got an 1982 gl1100. Just had Pistol Pete rebuild the carbs. Got it all back together and it runs really nice until I take it out on the highway. After running at a steady 55-60MPH for about 10-15 minutes it starts to lose power, starts to misfire. So I pull over and let it idle for 2-3 minutes and it's back to normal, no problems. I can do this over and over. Runs good for 10 minutes, then misfire. Let it rest then it's back to normal.

I thought it might be fuel-starved from a clogged gas cap so I ran it with the gas cap loose and that didn't help. Could it be a petcock issue? Fuel pump maybe? I don't know what it is but I have a feeling it's something really simple. At this point any suggestions would be welcome and appreciated.

[Lucien Harpress]

It may be swollen gaskets and o-rings in the carbs themselves. Had the same issue on my 1000- turns out the main plenum gasket had swollen the fuel passages nearly shut. Replaced with a Randakk viton gas let, and all is well.

[Track T 2411]

You could try to duplicate the misfire while on the center stand. This may help to isolate it to a specific cylinder as well as allow you to distinguish whether it is fuel or ignition related. Use a large fan on high blowing directly on the radiator to help keep it from overheating. You may find you have a coil issue. My 2 cents...

[zman]

Sure sounds like it is starving for fuel, have you tried switching to reserve when it happens?, check the fuel cap to be sure it is venting, a test would be to remove it for a ride and see if it cures the problem, cap should vent inwards and not let air out but some have drilled them out, just will smell like gas while riding.

[RB]

+1 on gas cap..easy to check run it with gas cap not locked down. If that fixes it soak the cap in vinegar over night and rinse it off or quicker 5 minutes muractic acid 50/50 with water.

[chowell]

Ran it on the center stand at 4000rpm. After about 10 minutes it started to act up. The very first thing it started to do was backfire out the tail pipe. A lot. Then it just ran rough. Rough idle. Loss of horsepower. Running with the fuel cap off is no help. Petcock ON or RES is no difference. Shut bike down and pulled the plug wires. Getting good spark. Let the engine cool. Now it runs rough all the time. I should get a piece of fuel line and a gas can and just run some gas straight to the fuel pump to eliminate the tank, petcock and fuel filter. Just to see. Otherwise, I'm out of ideas. I just paid around $800 to get the carbs rebuilt so I'm hoping that's not the problem.

[zman]

Sounds like a plan, I would run a filter from the auxiliary tank just in case, wouldn't want to get anything in the fresh rebuilt carbs. PP does great work, doubtful it is the carbs, there are 2 ignition ignitors that get hot after awhile running , wonder if they could be failing, must be a test for them, also a resistor on the coils, check coils for cracks...if it isnt fuel something ignition is heating up and failing.

[olchris]

Are the coils you are running "good", new? or are known to work well under normal operating (temp) conditions..? The ballast resistor might also be faulty if breaking down when hot!

[scootsx2]

+1. If you are confident that you have unobstructed fuel flow (you did clean your tank and the rest of the fuel system while the carbs were being done, didn't you? Hate to see fresh carbs get contaminated right away.) I would take a long hard look at the ignition system.

[Track T 2411]

The ignitors are under the false tank on the battery side of the bike. They are bolted back to back, and are gray and red, IIRC. The back side of them is filled with a tar-like goo that can melt and drip out if the ignitor begins to fail and overheat. You may see some of this goo on the frame below the ignitor.

If you are going to bypass the fuel tank, etc. I'd bypass the pump as well. The pump diaphragm could also be part of the problem unless it's new. The pump can also catch debris...

[jdvorchak]

Just my 2 cents. Since you have eliminated the fuel delivery problem I'm leaning toward coils. But first measure your voltage at the battery terminals while it's running just to make sure you have 14.2+ volts at highway speeds.

[chowell]

THANKS to everyone for the tips. Now I've got a troubleshooting tree to follow. I'm going to take her apart and try some things. Will be back with the results.

[chowell]

Installed a new fuel filter from Randakk.
Drilled hole through the gas cap.
Installed new Dynakek coils and new plug wires.
Symptoms are still the same. Runs for 10 minutes then starts to stumble.
I have new (used) spark igniters on the way.
Will be back with another report.

[Sagebrush]

Have you looked inside your tank with a flashlight? Its best to remove the sender unit to get a clear view (make sure the tank isn't full). You wouldn't be the first to marry a fresh rebuilt carb set to a contaminated fuel system and immediately plug the carbs with debris from the tank.

[Rat]

Who WAS the first .......?

Gord