ORIGINAL: Rcpilot

I think the low speed needle is too rich.

"It starts easily" most engines with a properly tuned low speed needle will be a little more work to start.


Do the following with a warmed up engine:
Run it up to full throttle and hold it for 10 full seconds.

Drop throttle to 1/2 throttle. If it's still running clean, start dropping throttle 1 click at a time. You can feel each click on your TX. Drop it down 1 click and wait 10 seconds. If it runs clean, drop another click.

You will reach a point where it will start to miss or burble. Shut it down and lean the low speed needle a TINY bit.

Start over. Run to full throttle for 10 seconds. Drop it down to 1/2 throttle. Now back it down 1 click at a time. Wait 10 seconds. As long as it runs clean, continue to drop 1 click every 10 seconds.

Each time, you will be able to drop farther and farther from 1/2 throttle before it starts to burble.

Stop the engine and lean the low speed needle when it burbles. When I say to lean it, I'm talking about 1/2 the thickness of the slot in the mixture screw. We're talking about a blonde *!@^% hair. Just a TINY bit.

Eventually, you will be able to run it all the way up to wide open and hold it for 10 seconds. Drop to 1/2 throttle and then back it down 1 click every 10 seconds until you are at idle speed. If it runs clean all the way from 1/2 throttle to idle, you're done. Adjust the endpoint on your throttle servo because as you lean the low speed needle the engine will pick up speed. Adjust the endpoint until it idles where you want it.

ALWAYS go back and check your high speed needle after making adjustments to the low speed. If you leaned the low speed more than about 1/8 turn, I guarantee it effected the high speed (leaned it). Run the high speed in until it peaks RPM. Back it up rich about 200RPM. Go fly it.

It sounds to me like you're running 100:1 oil. 1 1/4oz of oil in a gallon of fuel? Or was that 2oz of oil?

I'm sure somebody will come on here and say I'm an idiot and you'll burn your engine to a crisp if you follow my advice and run it wide on on the ground for that long. This is how I tune all my gassers and I use 40:1 mix. I've NEVER cooked an engine. The guy who taught me this method of tuning (Tony from Pueblo,CO. flying field) isn't burning up his engines either. I've read others mention this same tuning technique on these forums. If it cooked your engine, you didn't have it baffled right or you weren't running enough oil......... or BOTH.