GS850G Cuts out randomly

[Guest]

I have an 81 850G that seems to be cutting out at random times. However, when you start it again it comes back to life no problem. This problem seems to get worse with colder weather. This morning in 55* temps I was able to start the bike and hold the idle up without any help from the choke. Also I noticed at stoplights it would smell really rich. It would happen at all engine speeds and all varying loads. The bike runs great except for it gets about 35mpg and it cuts out randomly. Yesterday I road it a couple hours around town and it did it once on the way home. This morning I road it to work for 20 minutes and it did it 5+ times. I pulled the plug wires while it was running and noticed 2-3 didn't have as strong of an affect that 1-4 did when I pulled it. Does this mean maybe a week coil on its way out?

Things done so far:
Adjusted valves
Carbs dipped and cleaned per bikecliff
Tank cleaned
new plugs
cut the wires back and reinstalled spark plug boots
synced carbs on bike. Idle screws 2.5 turns out.
Compression test: even across all cylinders

[Brendan W]

Sudden changes tend to be electrical, fuel related ones are more gradual - if that makes any sense.
Could be a coil but before condemning it I would check out the ignition wiring. First off what voltage are you getting at the lt side of the coils and are they the same. Second try wiggling the plug to the ignitor at idle and see if you can provoke a change in sound and have a close look at the wire from the pickups and see if it isn't rubbing on something, particularly the exhaust.

[Steve]

By "idle screws", I am going to assume that you mean "pilot screws" (sometimes called mixture screws).

Did you just arbitrarily set them to 2.5 turns or is that were they ended up after testing and some careful adjustment?
That is near where they "should" be, but each carb is different, so might need a slightly different setting.

When the bike "cuts out", does it just STOP, like somebody turned the key off?
Does it start to stutter, like one coil died, so the bike is now running on two cylinders?
Does the power just fade until it finally stops?

Carry a spark plug wrench with you. Next time it dies, look at all the plugs to see if one of them is fouling out.

You have done all the normal stuff that should be done, so this one is going to take a bit more detective work.

.

[81GS850]

I set them at 2.5 initially, tried to adjust them with the sync gauge connected. Everytime I tried to lean it out or richen it up it ran worse, so I left them. It stops running like someone shut the key off. You don't notice until you twist the throttle and keep slowing down. Pull the clutch in, start it with a little throttle and it acts like nothing happened.

[81GS850]

Also pulled the plugs last night in the garage. The metal ring showed black soot, the top porcelain was tan/dark brown. To me the bike is running rich at idle and slightly rich all over. But could be cause of a weak spark? Also could I have the butterflies closed too much and then have it too rich allowing it to run? Maybe open the butterflies and lean the mixture?

[81GS850]

Ok so at work yesterday checked the pipes and all seemed to evenly be producing heat (used an IR gun). Pulled the # 2 boot and rethreaded it onto the HT lead. It hasn't died again... We'll see what happens. Also wiggled some of the wires coming from the pickup and going out of the ignition box.