Hi, I have a 1993 60hp 2 stroke, 3 cylinder engine which is running rough. Symptoms - lacks power at full throttle. When running normally, revs at 4,500 rpm at full throttle. When running rough can only get to 3,500 rpm or less. Cuts in and out i.e. mainly runs rough but occasionaly fires properly and goes back to 4,500 rpm at full throttle - doesn't last long though. I suspect only running on 2 cylinders and firing occasionaly on all 3. Idles a bit rough but ok - problem seems to be most acute above 3,000 rpm.
Spark plugs are all new and have been swapped around. Same problem occured before changing plugs. Run engine with one spark plug disconnected to try and find out which cylinder is missing. Engine performs the same regardless of combination of 2 cylinders. Makes me think there is not a problem with a particular cylinder (rules out carby), but a more general problem which affects all cylinders. Have replaced external fuel line and bulb - made no difference. Checked fuel filter - no blockage there. Adjusted fuel mixture on each carby but made no difference. Have not checked fuel pump, cylinder compression etc. etc. I suspect it is more likely to be electrical problem rather than fuel - because it is an intermittent problem - engine runs rough but then suddenly runs perfectly every now and then.
What do you suggest I look at next?
Spark plugs are all new and have been swapped around. Same problem occured before changing plugs. Run engine with one spark plug disconnected to try and find out which cylinder is missing. Engine performs the same regardless of combination of 2 cylinders. Makes me think there is not a problem with a particular cylinder (rules out carby), but a more general problem which affects all cylinders. Have replaced external fuel line and bulb - made no difference. Checked fuel filter - no blockage there. Adjusted fuel mixture on each carby but made no difference. Have not checked fuel pump, cylinder compression etc. etc. I suspect it is more likely to be electrical problem rather than fuel - because it is an intermittent problem - engine runs rough but then suddenly runs perfectly every now and then.
What do you suggest I look at next?