I bought a brand new $430 (yes it's expensive in Norway) OS 91FX from Norwegian modellers in Norway, two months ago. Since I'm new to RC planes and glow engines, I've now used about $60 to sort out my problems with the engine using the advice from Norwegian modellers. Now I've found the solutions to my problem myself, thanks to this forum, and it seems that I have to use another $50 to get rid of my bubbles. This is just because they sold me an old engine. Who do you think should take this extra cost? I think its best to have an expert opinion on this problem before I confront them. This is one of Norway's largest hobby stores, so I believe they have heard about the problems with this engine before.

EvenK.

This will solve your problems:

OSMG6997 26582900 VALVE ASSY 40-65LA
OSMG4078 29057000 COVER PLATE 91SX-H
OSMG7152 26582931 NEEDLE STAY 91FX 65LA

I've figured out that myself also after reading this forum, but thanks for helping me out with the partnumbers..