get your engine warmed up and pinch the fuel line at the carb to block the fuel... if the LSN is set right it should rev up slightly for about 2 to 3 seconds and die.. if it revs really high for more than 6 to 10 seconds and dies your lsn is rich..

I would make sure your LSN settings are right before you go tinkering with the clutch.. If the LSN is good then start by checking the internals of the clutch, see if there is any drag, check the bearings.. if they are shot they will heat up and expand and can bog your engine..