backfiring and sputtering

[rudedogg54]

My 78 XS1100E suddenly started sputtering and backfiring. It runs ok untill it warms up then it backfires, sputters, dies out. It seems to only affect the left two cylinders. Could this be my coil going out, or maybe the balist resistor. I didn't start having this problem untill after I had run out of fuel. Could this be from sedimet from the tank pluging the carbs? I don't know, at a standstill. any help would be greatly appreciated.

[strom]

If the bike runs OK through the whole rev range when cold, then we can exclude the carbs as a problem.
Might be coils or spark plugs.
Check the pick-up connections, but that's a long shot...

LP

[sixtysix]

Probably not the ballast resistor, that is only taken out for starting, to allow full voltage across your coils, if it was it would affect both coils not just one, could be a coil, but would likely affect one cylinder on either side. Maybe a bad black-box (ignition module)?

Here is a real long shot, fuel line is kinked or degraded inside and the addition of heat causes it to almost stop flowing......since it happened after you ran out of fuel, I would look at cleaning or checking petcocks and lines for junk....are your in tank filters still there? If not maybe something is stuck in a line or something.

[Mike Hart]

Dave, have you double-checked if it's reallly the two left pipes that are cooler than the 2 right ones?

Coils and black box transistor failure take out 1&4 or 2&3.

If it IS the two left, I suspect some kind of fuel prob. Are your fuel hoses stock? If they've been replaced, are they near enough to the engine that they could kink when heated? Are you running filters?

[rudedogg54]

I did some testing that I should have done from start. #2 & #3 not firing. Bad coil. Trying to find replacements. Dealer wants an arm and a leg for each one. Inputs on mine tested ok (primary) but high reading on secoundary (plug wires) output. I believe replacing the coil shoud do it.

[Mike Hart]

Not conclusive - could be pickup coil prob. Have you checked the
ingition troubleshooting tip?

[rudedogg54]

Checked the pickup coil. No signs of streching or breakage of wires. According to manuale, the reading for the secoundary is out of range. To high ohms. Going to pick up coils in about thirty mins. Will know for sure in a hour or so. But believe have found the problem. Keeping fingers crossed.

[rudedogg54]

Just wanted to say thanks for all the help. Replaced the coils and a weak fuel line that would kink when hot. Runs runs good now but will run even better after i get a color tune. Thats next on my list. Thanks again everyone. Yall are great.

[sixtysix]

Originally posted by rudedogg54
According to manuale, the reading for the secoundary is out of range. To high ohms. Going to pick up coils in about thirty mins. Will know for sure in a hour or so. But believe have found the problem. Keeping fingers crossed.

Remember the Manual is wrong (sort of) the resistance they give is with the caps off! (Not on like they show) Don't know what manual you have, so not sure if this applies.