Sporadic lack of power

[Guest]

Hopefully someone can help me puzzle through this. My daily driver, 1979 GS850G, has been basically trouble free for the last 8 years and 50,000 miles. Lately, within about 10 minutes of starting out, it may act like it's losing power, maybe running on two cylinders. I have to downshift to 4th or 3rd to get up a hill while it's doing this. This only lasts for about 5 minutes then power comes back like nothing ever happened. I've checked fuel filter in tank, clean. Pulled carbs, clean, blew them out and checked floats and needles anyway. It almost acts like the carbs are getting starved but I don't see why. This is very random, may happen some days, some days not. Thanks for any ideas.

[BigD_83]

Perhaps it IS losing power on two cylinders, as in, you have something starting to happen with one of the coils.

[bjrpkr]

would a coil go out like that or would they just quit? My experience with electrical components is they work or they don't.
thanks

[Steve]

Not everything is quite so "digital" in nature, some actually show signs of impending doom.

Coils are notorious for failing when they get warm. It is unusual, though, for them to come back into play without cooling off.

Another possibility for your problem is a clogged vent in the fuel tank. Next time it slows down, try opening the cap, then closing it, to see if the bike will run any better. If it does, that will be the problem, not the coil.

.

[bjrpkr]

Thanks Steve, that had crossed my mind. Just trying to figure out how to crank the cap with the key in the ignition while driving! Worse than texting! I think I'll at least pull the vent off next time I'm down to an empty tank.

[koolaid_kid]

It takes two keys. Use one of your spares, just leave it in the cap while riding.

[Steve]

I think I'll at least pull the vent off next time I'm down to an empty tank.

What vent?

The tank vents through the gas cap.

There are three hoses that go to your tank. Two of them go to the petcock, they are the fuel supply and the vacuum line to "turn on" the petcock. The third line goes to an assembly under the tank. Although it might look like a "vent", it is actually a drain line from the safety funnel that will catch anything that leaks from the fuel level sender and directs it away from the top of the engine.

As long as the petcock is not in the PRIme position, you can remove any of the hoses at any time, regardless of fuel level in the tank.

.

[Nessism]

Been keeping up with the valve adjustment?