1 Misfiring cylinder 2 and 3. Wed Jul 20, 2016 7:16 pm
ChocolateFrog
active member
Hello all.
I've recently purchased (19th) a 1987 k100 that's only running on 2 cylinders. I've been doing a fair bit of swatting up on the 'flying brick' but still have lots to learn. I'm reasonably mechanically minded but my electrical knowledge could be better.
I've seen there are a few threads on here already regarding misfires but they don't seem to relate exactly to what I have. Hopefully once the cure is found this thread might help a fellow K owner in the future.
Situation so far. The bike runs but only on cylinders 1 and 4 (looking at the head L to R). Max speed is 60 mph and it will not go over 4000rpm.
What I've done. Checked plugs (changed by previous owner) as expected 1 and 4 look ok, 2 and 3 wet and black. They're NGK's so I've ordered some original bosch ones as I read somewhere they may be better. There is spark to all plugs but it seems weak but that could have been the intensity of the sun today.
HT leads checked. Also look to be in good condition, resistance on all 4 looks as it should.
Coils. Replaced by former keeper for known good ones. Resistances are as they should be visually they look good. No witness marks on the crankcase to see.
Its got a recent AGM battery looks almost as big as the one in my car.
Cleaned up the main earth point under the tank it had grease on it which I think may have been insulating it (not sure if bad?)
Checked outputs from the EFI under tank all seems good.
Hall sensors are getting power and ground. Haven't been able to test them bit they've also been replaced by the prevuous owner.
Removed and cleaned the AFM. The flap moves freely, visually the factory seal is still intact and the resistance across the temp sensor is correct.
Checked for obvious vac leaks, hoses I can see all look ok.
Checked the fuel filter was not blocked and is installed the correct way round.
Lastly the choke light stays on permanently and the cable is slack despit being on the end of its adjustment, not sure what's going on there.
I'll put it back together tomorrow to see if I've cured it but if not any other ideas? I'm getting near the limit of my knowledge.
Cheers
Paul
I've recently purchased (19th) a 1987 k100 that's only running on 2 cylinders. I've been doing a fair bit of swatting up on the 'flying brick' but still have lots to learn. I'm reasonably mechanically minded but my electrical knowledge could be better.
I've seen there are a few threads on here already regarding misfires but they don't seem to relate exactly to what I have. Hopefully once the cure is found this thread might help a fellow K owner in the future.
Situation so far. The bike runs but only on cylinders 1 and 4 (looking at the head L to R). Max speed is 60 mph and it will not go over 4000rpm.
What I've done. Checked plugs (changed by previous owner) as expected 1 and 4 look ok, 2 and 3 wet and black. They're NGK's so I've ordered some original bosch ones as I read somewhere they may be better. There is spark to all plugs but it seems weak but that could have been the intensity of the sun today.
HT leads checked. Also look to be in good condition, resistance on all 4 looks as it should.
Coils. Replaced by former keeper for known good ones. Resistances are as they should be visually they look good. No witness marks on the crankcase to see.
Its got a recent AGM battery looks almost as big as the one in my car.
Cleaned up the main earth point under the tank it had grease on it which I think may have been insulating it (not sure if bad?)
Checked outputs from the EFI under tank all seems good.
Hall sensors are getting power and ground. Haven't been able to test them bit they've also been replaced by the prevuous owner.
Removed and cleaned the AFM. The flap moves freely, visually the factory seal is still intact and the resistance across the temp sensor is correct.
Checked for obvious vac leaks, hoses I can see all look ok.
Checked the fuel filter was not blocked and is installed the correct way round.
Lastly the choke light stays on permanently and the cable is slack despit being on the end of its adjustment, not sure what's going on there.
I'll put it back together tomorrow to see if I've cured it but if not any other ideas? I'm getting near the limit of my knowledge.
Cheers
Paul