Hi

I'm just wondering if anyone else has experienced any problems with the OS 110 FSa engine. I've had two of these engines and the first one was extremely tight even after the run in procedure. The engine would die when I reduced the throttle for landings and after a time the engine just got tighter. I didn't understand why as the engine was run on the rich side and I never achieved optimum RPM. I sent the engine back for diagnosis and without any questions OS just replaced a set of bearings. The engine was much better afterwards but unfortantely several weeks later I had a bad crash with my plane and severely wrecked the engine.

At that I purchased another OS 110 FSa and this engine was easy to run in, and I haven't yet had a deadstick landing with it, after appx a total of 3hrs running time I was able to increase the rpm to almost 10000 rpm on a 14x8 prop. This engine has always been run on the rich side, can always see a good stream of smoke coming from the exhaust. However over the past couple of weeks I have started to hear some kind of knocking noise when the plane is in flight. I've not been able to locate the source of the knocking but I have noticed when I'm back in the pits and checking over the plane that there seems to be some kind of play on the prop/crank shaft of this engine. When I turn it so that the piston is at top dead centre there is quite a lot of sloppy movement, say around quarter turn of free slop play either way and it doesn't sound good. I'm concerned that this is my 2nd OS 110 FSa engine and that the bearings may be troublesome. As this is a relatively new model to the range of OS engines, is it likely there's some inherent problem with this engine model? Should I be concerned or is this normal for this type of engine?

Any help or views would be much appreciated. I'm a bit loathed to remove the from my plane yet again and send away for diagnostics/repair as this means loss of flying time yet again.

Thanks
Craig

I'm no expert but my opinion knocking = bearings.

Usually, knocking is caused by a too-lean mixture or too much load on the engine (a too-large propeller). The knocking is actually detonation, and can be heard above the exhaust note.