This engine has several hundred flights on it and the bearings need changing. On disassembly, the cam lobes also seem rough, not smooth and the backplate appears to have been scuffed on one side by the conrod which also has some scratches on the side of the bronze bushing. I have been using Powermaster 20% nitro/20%oil. Is this a mistake with too much nitro? When I reassemble the engine, what is the cam timing procedure?

If I decide to replace the engine, will the 160 twin mount be anywhere near the same bolt pattern?

Thanks for the help.

Rockythe enging

Over time, wear patterns do emerge with all engines. With an O.S. four-stroke engine, some wear on the cam lobes is to be expected after long-term use. Replace the camshaft.

To time the camshaft, you line the dot on the cam gear with the center of the cam follower when the piston is at top-dead-center.

It's normal for swirl marks to appear on the rear cover of nearly all single-cylinder model engines, 2 or 4-stroke.

The mounting pattern for the O.S. FS-120 Surpass is the same as for the 1.40 RX, but not the 1.60 FX.

Thank you for your help. I plan to replace the conrod as well as the cam. My question about bolt patterns was related to the ft 160. Is it neaer the fs 120?

Thanks.

The O.S. FT-160 is a two-cylinder engine, and has a very different mounting setup from the FS-120 Surpass, which is a single-cylinder engine.