OS FP 46. Years and years of flying and I've always had trouble with engines. Build and fly I can do but I must have a mental block on tuning engines. My question is, can a engine of this type be actually damaged by running too lean? Not months and month but in 1 day of maybe an hour of actual run time. I've got it at about 1 3/8 from closed now and it doesn't seem quite lean enough.

thanks,
Mike

i don't think an hour or so would damage it badly.. usualy it's over a period of time that it causes damage.

Sometimes when i tune my o.s. .46 when i get too lean it almost sounds the same as a too rich engine... almost like a sputtering sound.. or power loss.. did you try to back off the lean and go richer and see if it starts comming to life?

Ive got an OS SF 46 that is probably 10 years old (Ive actually have 5 of these they run so well). If you look at your instruction manual, I believe they call for 1 -> 1.5 turns as your base settings for the engine. So no, 1 3/8 turn sounds fine.

There are many ways to check the richness of an engine. The pinch test is one, pinching the fuel line and listening to a slight increase in RPMs to indicate needle settings. Listening to the pitch of the engine, and many more. Its not to hard, just takes a little practice.

clay

Thanks for the quick replies. I believe it's still just a little rich but my main problem was a fear to damage the engine if I run it too lean. Knowing that I can't damage it in a few minutes will help my confidence in turning in the needle a click or 2 more. The pinch test... I didn't know that one. Thanks again.

I wouldn't want to put in a lean flight with an OS 40 FP. I have 3 of these and they're great engines. Pretty powerful for their size, but these engines don't tolerate lean runs very well. Setting it too lean while adjusting, then backing off again won't hurt it, just don't run it for 2 or 3 minutes at a time that way.

I've always found the easiest way to test for proper settingis to lift the nose of the plane. ie, set the engine to what you think is right based on engine sound or rpm, then lift the nose to near vertical. As long as the rpm increases, your setting is okay. If there's no increase in rpm, or the rpm decreases, your too lean. (Same as the pinch test actually.)
Dennis-