The OS.61 in my Hangar 9 Alpha 60 Trainer just flat will not idle. The engine has probably 3 gallons of fuel through it total. I have been running 10% Cool Power (green) and #8 glow plug. The second to last time I flew it I had to dead-stick it in after it quit during approach on idle. Let's see, I have pulled the carb & remote needle off and cleaned them out the best I can. Took the carb apart down to the last screw. Blew everything out with compressed air. I replaced the fuel line from the remote needle to the carb thinking it might have a pin-hole leak. When we do get it to run at above idle, there are quite a few bubbles in the needle to carb line but not the tank to needle line. After sitting at idle for about 10 seconds it will load up and either quit then or there is a big hesitation going to full power. We changed the glow plug several times with no results. We fiddled with the idle screw numerous times with so-so results. This is an OS engine for crying out loud! It is made to run!

Any suggestions? I realize I am probably leaving out numerous details but it is something to chew on.

Thanks

sounds like the needle valve is leaking air into the fuel line.. got a spare needle valve ..if not they're pretty cheap

Sounds like an air leak in the needle valve and that the idle mixture is too rich. For the bubbles try putting a piece of fuel line over the needle valve to seal it.

Thanks for the responses. I am going to replace the o-ring on the needle valve (that's cheap). I will also try the fuel line over the needle valve idea as well. It has to be something incredibly simple and that I am just not picking it up.

There is also a fairly dependable way to adjust the lowspeed needle. After you've solved the air leak, it'd be worthwhile focusing on the lowspeed needle setting.

Probably not dialed in right