I have a 2003 wolverine that is really giving me fits.


-very black spark plug even after changing it and running it for less than 2 or 3 minutes\
- sputters alot when motor is working hard
-acts like it is not getting right air fuel mixture
- idles fine with no detectable misses

What I have tried:

Cleaned air filter
tore down carb and cleaned perfectly
replaced coil
replaced boot
replaced spark plug cable
replaced spark plug multiple times

HELP!...any suggestions? Thanks