Lightly missing

[cavehamster]

Howdy all.

My '80 GS1100 has a light miss. Hooking a timing light up to any coil wire shows me that randomly, the spark plug does not fire. I can hear it in the exhaust. However, the bike revs well and seems to have good power, but anytime the engine is at a steady RPM it misses lightly.

I recently had an issue with some rust out of the tank plugging up the tank outlet, so I cleaned that out, as well as taking off the carbs and cleaning out all the float needle inlet screens. Prior to this, the carbs had been completely cleaned and rebuilt. I'm uncertain now if the miss was there before my cleaning or not.

I just did a carb sync and have them all pretty much dead on.

I've been digging through the forum and have a few ideas. Perhaps I should be looking at adjusting the pilot air screws and etc? Or is there supposed to be a light miss? I have not removed the spark plugs to look at their conditions yet, but they have less than 40 miles on them. Perhaps I should take the carbs off and clean them a tad deeper? Is there anywhere likely to plug up due to particles getting past the inlet screens?

I'm also noting that cylinder number 4 is running a tad cooler than the others, about 50 degrees F cooler via my infrared thermometer. Maybe related? This was certainly happening before the rust issue.

[rustybronco]

The first things I would check are, plug cap to plug cap resistance for the 1&4 and 2&3 coils. then take a look at the plugs for evidence of fouling.

[duaneage]

Clean the carbs. they probably need it anyway. Sounds (pardon the pun) like a lean out is occurring.

[cavehamster]

I'll yank the plugs tonight and see what is going on, check out the condition of the intake boots and o-rings, clean the carbs fully, and attempt to tune them all the way through.

Wish me luck! Hoping to get it out to the drags on Sunday

[cavehamster]

Alrighty, I adjusted the valve lash, took off all the intake boots, cleaned them, no cracks, so I applied some grease and re-installed them. Tore into the carbs. 3 of the 4 had that little passage in the fuel bowl clogged, and one of them had a needle jet that failed to get cleaned when they were rebuilt, whups.

I was unsure of how to set the floats, as in, where to measure to. I measured off the tallest point, but they just spouted fuel when I filled them. Back off again, measured to the notch where the curve starts, 22mm, and they held fuel.

Fired it up, runs great! Something got fixed. Still need to do a carb sync again. Tore around the block on it, feels real good. Think I'm going to be able to hit race day after all.

Thanks all for your help and, in this case, encouragement to just clean it again and be done with it, hehe.