sometimes if the rings are stuck from carbon,,,a simple water injectionsetup canremove the carbon,,,i used an old washer bottle hooked upin the air intake tube,witha smallcarb jet in the endof the hose,but it sounds like your engine is tired,,,,water inj. lowers egt+more power too,had a button on the shifter toactivate it,,,i had all the parts laying around (a2 gallon washer bottle,hose,carb jets),,so the major expense was actually filling the washer bottle,,,,,,,,kinda like filling the gas tank of a honda doubles the resale value,ya know???