Really weird problem

[warnett]

1983 gl11oo. Hard to explain. Cuts out, misses at 3500 to 4500 rpm when leveled out. I can power throught it from a start. Starts and runs great except for this problem. If you stay on it, it will finaly get throught it and run great but right in that range it spits and
sputters. No matter what gear. Tryed differant carb set same thing. Swaped coil pak same thing. Changed pulse gen. same thing. When it does this can see black smoke from exhaust from cyl 1 and 2. Going crazy trying to fix this problem. Plugs 1 and 2 show a small carbon spot on Porcelain on the same place. Going crazy trying to fix this problem.

 

[zman]

Have you taken an ohm reading of the wires and caps? It sounds like a short or arcing if indeed your replacement parts were good. It`s a tough one. Also I would replace the spark plugs just to be sure.

 

[joedrum]

well 1 and 2 indicates iggy could be involved ...as is carbs ...and also take plugs out all the way around ..put kill switch to off position and spin motor with starter and ck to see it it has good push form all four cylinders with a thumb tester ...

 

[slabghost]

Check your vacuum and mechanical advance units. Last in this case because it involves taking half the bike apart to get to. Does your 82 do the same? If not try swapping the carb rack from the 82 on it. If the problem disappears it's a carb issue. I'd put in new spark plugs too. I've had even brand new plugs give trouble at certain loads. It is a weird problem indeed.

 

[2_Wing]

Strange indeed......weak spark, rich mixture, low compression or sticking carb slides come to mind. Sounds like youve done alot of component swapping to eliminate them.

Maybe bad plugs, wires, or caps for cylinders 1&2 or any and all ignition wiring or harness plugs....

Sounds like time for a compression test, resistance checks on plug wires/caps and a valve clearance check/adjustment.

 

[joedrum]

yes ... and its now possible to get greatest after market product for oldwing 1100s now ... the c5 iggy I am totally pleased with its perfect timing it provides to my bike