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My ’78 XS1100E has given me several years of relatively trouble-free operation in the time I’ve had it, which is surprising since the previous owners didn’t take very good care of it. At one point the bike developed a misfire while turning, and upon hard acceleration from low RPM, but this seemed to be cured by removal of the under gas tank tip-over switch, (which rattled excessively as if it had come apart inside – it seemed to click if even only slightly tilted.)
Lately though, the machine has finally developed a complicated problem… When the engine is cold, it still runs great. Idles well, accelerates hard with no misfire, and produces an enjoyable level of torque while carving corners. However, all of this goes south after the engine warms up.
Once the engine is hot, as I open the throttle from mellow cruising (about 2800-3600 RPM,) the bike begins to accelerate momentarily, and then drops at least one cylinder. The power loss is dramatic, and it could possibly be more than one cylinder. Once this power loss occurs, it continues, until I pull in the clutch and moderately rev the engine once or twice. By the second rev, the motor will clear up, and I can once again release the clutch and continue on… For a little while, until I try to accelerate again. This does NOT occur every time I try to accelerate but slowly becomes more prevalent as the engine warms up, and tends to happen up to about 50% of the time once the motor is hot. (As if it is getting worse.)
The vacuum advance is functioning, (how accurately I cannot say,) and the timing stays set. It doesn’t appear there are any vacuum leaks. The vacuum operated petcocks appear to be functioning as well. The spark plug wires do have a few weather cracks in the insulation, but there is no indication of arcing, (although this problem cannot be recreated at idle, only when moving and it would be dangerous to stick your head under the tank to look around in the dark.) In my experience coils tend to either be good or bad, and usually don’t produce intermittent problems… So I am starting to suspect a carburetor problem… Which is what I dread. Especially, since they seem to be relatively well synchronized and I’d rather not mess with them.
NOTE: When I first got the bike, it would drop a cylinder when wet, but this would ONLY happen when the bike was in gear. Put the wet bike in neutral and the misfire would stop, put the bike in gear, and it would once again drop a cylinder. Since it doesn’t rain too much around here, the problem seemed to correct itself before I looked into it too deeply, so I never bothered.
Any ideas before I end up opening up the carbs?
Lately though, the machine has finally developed a complicated problem… When the engine is cold, it still runs great. Idles well, accelerates hard with no misfire, and produces an enjoyable level of torque while carving corners. However, all of this goes south after the engine warms up.
Once the engine is hot, as I open the throttle from mellow cruising (about 2800-3600 RPM,) the bike begins to accelerate momentarily, and then drops at least one cylinder. The power loss is dramatic, and it could possibly be more than one cylinder. Once this power loss occurs, it continues, until I pull in the clutch and moderately rev the engine once or twice. By the second rev, the motor will clear up, and I can once again release the clutch and continue on… For a little while, until I try to accelerate again. This does NOT occur every time I try to accelerate but slowly becomes more prevalent as the engine warms up, and tends to happen up to about 50% of the time once the motor is hot. (As if it is getting worse.)
The vacuum advance is functioning, (how accurately I cannot say,) and the timing stays set. It doesn’t appear there are any vacuum leaks. The vacuum operated petcocks appear to be functioning as well. The spark plug wires do have a few weather cracks in the insulation, but there is no indication of arcing, (although this problem cannot be recreated at idle, only when moving and it would be dangerous to stick your head under the tank to look around in the dark.) In my experience coils tend to either be good or bad, and usually don’t produce intermittent problems… So I am starting to suspect a carburetor problem… Which is what I dread. Especially, since they seem to be relatively well synchronized and I’d rather not mess with them.
NOTE: When I first got the bike, it would drop a cylinder when wet, but this would ONLY happen when the bike was in gear. Put the wet bike in neutral and the misfire would stop, put the bike in gear, and it would once again drop a cylinder. Since it doesn’t rain too much around here, the problem seemed to correct itself before I looked into it too deeply, so I never bothered.
Any ideas before I end up opening up the carbs?
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