I've got a Thunder Tiger F.91S 4 stroke that's almost a year old. When flipping it, the engine seems to have less than one third the compression of my buddy's .91 Surpass. It's only got 2-3 gallons of fuel through it. I've adjusted the valves to spec. with no increase in compression. The engine starts well and runs well but is not as powerful as other .91s. Something's wrong here.
What could cause the compression to drop with such little usage and what parts could I replace to increase it? Is there an easy test to check it? Expo