skylark-flier

I've got an OS-40LA mounted on its side in a GP J3 Piper Cub, using a pitts style muffler and pressured tank and cool power 15% nitro fuel. When it was new (4 yrs old now) it ran just fine but now I'm having a bear of a time keeping it running at less than 1/2 throttle, especially on approaches and landing. I'm pretty sure it's an idle-screw (bleed) problem - it's probably WAY off.

Where should I re-set it to get something of an idle again? Getting rather tired of dead-stick landings (have to walk too much to retrieve the plane).

Thanks.

Dave W.

kersplat

How's your compression? If it is worn out, it won't idle.

skylark-flier

Yeah, compression's good.

Bax

My Feedback: (11)

The O.S. Max .40 LA engine should be properly-tuned at full throttle before you start to work on the idle. The air-bleed screw should be initially positioned so that it blocks the air-bleed hole 1.2-way. Turn it in to richen the low-end mixture, and turn it out to lean. If that won't work, then it's possible that the compression fit has become a bit low. The idle is the first thing to go when the piston/cylinder fit starts to wear out.

skylark-flier

Hey, yeah - it's quite a bit better now, once again. High-end was just fine but I think I had too much air on the low-end, it's set at about 1 1/3 turn (was nearly 2 turns) from closed now and the engine idles rather nicely again. Thanks a LOT.

Dave W.