highlander84

I was wondering if there is sure fire way to test the compression on a TT39. I think I need a new Ring, but wanna make sure replacing it will help. When I rotate the engine by hand I can hear air passing the ring. it still runs but seems very underpowered when I fly. Anyways thanks for the info...

Smashmaster

It's been my experience that a bearing will fail before the ring will. It's very simple to pop the head off while the motor is out. You can look for slop in the piston, Usually the piston will get scored before the ring will fail also, So if compression is the source of your problem slop in the piston with the head off should be fairly obvious. If you still wonder at that point, just take the 4 bolts off the back cover, and you can get the piston out. But at that point you are pretty much comitted to at least put a ring in it. Also the pin that keeps the ring from rotating wears so it would probably need a piston also. Just mark everything before you take it apart. That way there aren't any questions about which way something goes whaen re assembeling it.
Fred

highlander84

there is no slop at all. I know i overheated it when i was still learning and im fairly sure the ring is shot thus letting air by and lowering its proformance. But good info. Ill probley just replace it to see if that was indeed the problem.