On my stump grinder. Over the last 30 years three rebuilds. Hit the starter, three revolutions starts right up and go out and grind stumps. So the problem Im having is it appears to be running way too rich. Put my finger and wipe on the exhaust pipe a lot of black soot. Yesterday check the timing all is good. Took PB blaster brake cleaner which is Volatile ,how I know that is I sprayed some on the bench and it burned. While its running sprayed all the manifold gaskets no change in RPM until I sprayed the throttle shaft linkage and then got some noticeable difference so I have a leak there. Could the oil bath filter element be so plugged up causing it to suck more fuel than air..