pbeck14

I have an OS 46 AX engine powering an LA racer aircraft. It runs with an 11x6 prop but I seem to have difficulty in getting the engine to run smoothly on a consistent basis. In particular, what occurs, is that it starts ok and at full thrust gives about 12000RPM on the tacho. You then throttle it back to idle, carry the plane to the takeoff point, but then, when you increase power to take off, the engine will hesitate or even stop. Also, once airborne, it is not uncommon to hear the engine lose power at times or run a little rough. We use new fuel which is filtered and the engine itself is quite new.

I adjust the needle valve to max RPM and then back it a little to the rich side. The only other adjustment is a very small inset screw on the carb barrel...I wonder if that could be part of the problem. Does anyone have any suggestions on what to try to get this engine running smoothly at all times and throughout its power band? It does have a very good reputation for doing so.

Many Thanks

Paul.

speedair

Try checking all the fuel lines for cracks and if all look ok try re adjusting the engine to max rpm then turn it 1/4 of a tyrn rich if the problem still continues id try to make it a bit leaner or replace the glow plug

Bax

My Feedback: (11)

The small screw inside the throttle arm is the idle-mixture adjustment. Likely, you have it too rich. Lean it a hair and see how it goes. You can adjust it using the "pinch test". When the engine is at idle, pinch the fuel line. If the RPM tends to increase, the engine's a bit rich. If it tends to drop or quit, the engine's too lean. Usually, though, a too-rich midrange or hesitation on throttle-up indicates a too-rich idle mixture.