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New OPE Member
I have a Stihl KM90R power head with an exhaust valve that refuses to seal. The unit is 4 years old and has less than about 60 hours on it. I have been using a 24:1 gas/oil mixture with non-synthetic oil. The exhaust valve turns freely when unsprung but will not seal after several hours of soaking with Mopar heat riser solvent , and then with SeaFoam. Any suggestions for a better solvent or other ways to clear the seat?