O.s .70 surpass 2
 

I bought this engine a year ago! It keeps dead-sticking in my twist after 3-d aerobatics like tr's or spins (I did try opening the needle valve it. I;ve even put a perry pump on there and it sort of helped but was to heavy! Also I put it in my twist with an apc 13x10 and it's not really vertical unlimited as much as it should be. If I lean it for power it backfires like all 4-stokes. Does my problems have anything to do with the rockers. Does anyone know why my engine is this bad? I know a lot about gas and two-stokes but not 4's. Please help?

RE: O.s .70 surpass 2
 

It sounds like the valves need to be adjusted. You should not have backfiring problems. You said "like all fourstrokes", yet I have never had a fourstroke backfire after being adjusted properly. Only in the very early stages of breakin if you get a fourstroke too lean will it backfire, if adjusted properly. Hope this helps.

Lachlan

RE: O.s .70 surpass 2
 

13/10 wouldn't be my choice if looking for max thrust, as in best vertical. the steep pitch could be stalling it at low speed.

RE: O.s .70 surpass 2
 

A 13x10 is WAY too much pitch for this engine.

I have had several 70 Surpass engines, and still operate an older one. 13x6 is the best general-purpose prop for most applications. For your 3D work, try a 14x5.

And if it is back-firing, it is too lean; period. That can be caused by your needle settings, or overheating from the load imposed by that prop.

RE: O.s .70 surpass 2
 

Ditto on the too lean. As a Twist owner and an OS FS70S2 owner, (not on the Twist) put an APC 14-4W on that engine and have fun! The Twist doesn't need speed and you'll have vertical like crazy! Mine turns 9800 RPM with this prop.

Have fun!