I have an OS-61FX with a gallon of gas thru it. running a 11x8 prop. She transitions excellent,,,idles great,,cant complain at all,,,,,,,,,,,,,,,,except the engines has a knocking sound at anywhere from half throttle to full throttle,,Ive tried leaning.richening and everything in between,,,,cant get rid of it.. I use Tower premium 2-stroke fuel,,and run an OS#8 glow plug. All my other 2-strokes dont have this problem.. Is this something I should be concerned with..or is the engine lobeing or is something about to go on it. Ive also tried different size props,, to no avail.

I would highly appreciate any insight on this condition.


[sm=spinnyeyes.gif] Thanks a million--you guys and gals are the greatest JIM

I have a couple of those OS Max 61's on planes right now. Neither one make any knocking sound. If the piston isn't hitting the plug, then maybe the wrist pin was bent. Sometimes, when using an electric starter, if the engine is flooded, and enough fuel gets trapped above the piston, you can bend the wrist pin. I might just open the engine up and take a looksee. It only takes a few minutes.