That engine uses the 32 853 12-S carb. Not cheap so I would start with a carb rebuild, but also need to check to make sure there aren't other things going on also. Compression, valve clearances, spark. Also I would pull the blower housing and check the part numbers on the ignition modules to make sure they match, and to make sure somebody hasn't tried to convert the DSAM or DSAI to the fixed timing ignition modules instead of the MDI modules.