I have a 04 MC 900 EFI and the PTO side fouls out when ever it is warmed up however the other side looks fine. Both have spark and I have ohmed all the sensors, coils, stator, etc. it appears fine. I did the voltage test on the stator and some are not within tolerance however I don't know if I am seeing the peak voltage because I have a digital ohmmeter that doesn't show changes quickly. The stator shows no damage. Does anyone have any suggestions? Only thing I haven't checked is TPS but I would guess that it would do both cylinders and not just one.
Anyone know why only one cylinder fouls out?
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diggerdown
Well-known member
Check the compression. If thats good, switch the plugs wires from one side to the next, then switch the injectors side to side, then check the reeds.
Could it possibly be a bad PTO engine seal ?
" Travel is fatal to prejudice"
" Travel is fatal to prejudice"
I switched injectors and it did not follow injector but haven't done the spark plug wires yet. They did ohm out with specs. As for the reeds, I did look at them without taking them out. They look okay. Compression is good. I was wondering if the stator will only affect one plug but not the other? Also, it gets bad only when warm, if that matters. 
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diggerdown
Well-known member
Stator would not be selective on a certain cylinder. Did you check the comp. when it was hot? Try switching the plug wires from one side to the other. Could be a coil that is weak on one side. They both fire at the same time so it won't anything to try.
I'll check compression this week and try the spark plug wire swamp next time I am out.
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bigbull
Well-known member
If you have adequate spark and good reeds then look to the throttle body. Do you have a EFI aftermarket controller installed? IF not, then check the injector on that side. If you do, well then we can narrow that down right quick. Also the exhaust valve, make sure it is operating efficiently, not sticking and the cable is in good shape.
BB
BB
im having the exact same problem with my polaris indy 500 also with EFI, i put new plugs in on sun morning and after a few hours of riding i checked the plugs. One was light coffee brown and one was dark coffee brown and a little oily. I checked the compression and both cyl. were 125 on the nose and the motor ran strong all day.
