I have a new ys 120 on my pro edge,since installing the engine it seems it has never ran correctly,now if i go above say 1/4 throttle it stalls,ive gone threw just about every adjustment scenario i can think of,does anyone have any ys knowledge they could lend?I used a 16-4w prop so not to cause over reving,i ran the motor rich,ive canged the plug numerous times.What have i done wrong?Is the bottom end messed up?Thanks.

I was just looking on this forum and saw you thread. If I were you I would go and search for the YS club. There is a club just for people who know A LOT about YS engines!!!

rc-plane

Which version of the 120 is it ? Some years back , Rick Matte of YS( then a separate company) posted trouble shooting techniques for the 120 versions and the 140 FZ. I have a copy somewhere .I believe he now works for Airtronics. Check out NSRCA.org ( pattern association ) and also post this question on the pattern forum on RCU. Remember to say the version- NC, AC, SF, FZ , etc.

Go straight to the NSRCA.org. site. Go to links, Grotto2 pattern , scroll to engines. Rick Matte's YS 120 trouble shooting guide. The man knows these engines and you will have success.

............or take it to the "YS Support" forum. Troy and David live and breath these engines.

This much I can tell you that 16 x4 W is not enough prop for any 120 YS engine a 17x4 pushes the envelope for RPM's .
Theres several things that could make your engine do what its doing,
The Glow Plug
Check Valve
Air leaks
Fuel Tank plumbing
worn out needle valve assy.
Or just plain out of adjustment.
If you can't get it going by doing the simple things I would send it in to YS if your not that familure with there engines.