I have 3 older (exagerated!!) OS engines that I can't get to run. I haven't tried them for about 3 years now and just put them on the stand this last weekend. They are a 60 FP, a 61 SF, and an SR 60. I have an OS engine book form 1990 that goes back quite a ways and it doesn't even mention the SR series, just the FSR.
The SR & the FP have plenty of compression so I'm not as worried about those 2 as the SF. I had this on my senior telemaster 4 years ago. It pooped out on a very hot summer day-maybe I ran it a little too lean-I'm not sure? This one has very poor compression. I took the head off and removed the back plate and cylinder liner. The piston ring seems to be seized in the piston. I tired soaking in carburetor cleaner, spraying with the aerosol carb cleaner and letting it sit-all of the usual things that worked for my other engines. I don't know if I can even find a new piston ring for a 61SF? The other thing was how do you get the rod off of the crank? Do you heat it up, or is there a special trick or tool to release it from the crank? It will slide back about 1/4th of the way then stops.
This engine did power my telemaster around quite well but not like an FX. I bought this one used a long time ago then used it myself. However, the rest of it is in good shape and I would like to keep it if I can. Thanks for bearing through this with me. Tracy.

The 60SR is really a 60FSR and was the forerunner of the 61FSR. The case was used in both the 60RSR and the 60FSR so all it has is SR on it. The RSR was a rear induction and the 60FSR's were front inductions. The rear bearing is smaller on the 60 than the 61 as well as several other changes. As far as removing the rod, it's stuck with varnish and oil to the wrist pin. heat the engine to about 300 degrees in the oven and it should soften the varnish and hardened oil and allow you to slide it off. How did you get to the ring without getting the piston out of the case?

There are several sources for a ring. You might try Tower first. Frank Bowman will make a ring for that engine at a reasonable price.

Good Luck.

I took the head off then the cylinder liner. The ring seems to be seized all the way in the piston wall. I'll try heating it up tonight. THanks, Tracy.

Did you get the piston out of the case?

I did. THe oven method worked. It also freed the ring from the piston. I reassembled the engine and put a little marvel oil in the cylinder. The combination of the oil and the freed up ring helped the compression a little but not much. I'll get a ring from Frnak Bowman. Thanks for help Pornto. Tracy.

Pornto? Is that the Lone Ranger's perverted sidekick? Glad I could help you get the engine apart. Even with low compression it should probably run OK. If the idle is poor then you probably need a new ring. I have several engines with less than great compression that run quite well. An electric starter makes starting them easier.

Sorry about that Pronto! I guess my hands-fingers were moving faster than my brain! I put the engine in the oven for about 5 minutes and the con rod came off of the crankshaft, and the piston ring came free from the piston. I put it back together and ran it-it was hard to start at first. I had to readjust the needle, but it ran about like before. This engine was never a powerhouse ( at least not since I've had it) but was always dependable and consistent. Its just like it was. Thanks for your help, Tracy.

Hi,
I know this post has wiskers but I am trying to help out a good flying buddy that crashed his OS 61 SF. His has very little run time on it but he cracked the muffler and case. Maybe the case could be saved but he tore the muffler screws out baddly. Cracked off the metal over the rear screw.
Any how I sent you a PM. I guess when you hunting old parts old posts get bumped
Thanks,
Ozmo01