flybyme

Hello Bax, I have a 120fs surpass III that will not reach max rpm.........I have run 4 tanks through it, the first two, I reached full throttle during run-in........the leaning and richening procedure. After that, every time I tried to go past 3/4 throttle, the engine bogs down........it will speed up again if I decrease throttle to half or below.........idles well. I have tried adjusting the idle-mix screw, leaning and richening, mostly leaning but not wanting to go past 1/2 turn from the closed position. Could the rockers need adjustment this soon, or what could be my problem? It flies perfectly well at half throttle and below, just bogs down when I go above.

Bax

My Feedback: (11)

If it's the FS-120 Surpass III, then it's the pumped version. Where do you have the high-speed needle set? Your note didn't say that. Please put the needles at the recommended starting position, pre the manual, and start from there. They should be rich settings. Also, please note that pumped engines do not get leaned to peak and then richened. You lean them and leave them there! You want the high-speed needle set as lean as possible without detonation or RPM drop.

jp928

My Feedback: (5)

Flybyme, If it surges up and down when left at full throttle, it sounds like the regulator is dying. Usually this doesnt occur until a lot of flights (in mine and others experiences), but you never know. Try re-tuning from scratch as Bax says, and if that doesnt fix it, look at the regulator cover. If its not sitting absolutely flat on the casting, its done for. OS sell a new diaphragm and cover kit, with a thicker more rigid cover that should fix this problem. The part no is somewhere in this section in a post undermy login.

jp , BTDT

ton2di

My Feedback: (182)

My OS 120 SurpassIII pumped attains peak rpm at around 4/5 turn from fully closed. I'm turning an apc 15x8 at around 8,600 rpm. Low side is a bit rich with the presence of heavy smoke at above idle. Fuel is 15% coolpower.