Andy,

My first diesel engine was a McCoy .049, purchased soon after they were introduced.

I taught myself how to start and run that diesel engine, on fuel I mixed in the basement. While I was teaching myself, and several friends to fly control line with a Walker Firebaby, I noticed the engine was getting harder to start. When I pulled the screw on head muff, I found a mess of rubber pulp gumming up the top of the contra piston. Pulled the contra piston out, and discovered that the O ring was worn flat on the outside! It was a soft white material back when silicone rubber was still a dream, so I'm pretty sure it was rubber.

I wrote the McCoy company, and asked if replacements rings were available. The response I got was a nice letter, and a small bag of new O rings at no charge! Never did use them all, and sent them to an English pen pal along with the engine shortly after.

My pen pal was a master machinist, and made a new metal contra for the McCoy, and was very pleased with it.

I now have three McCoy .049 diesels to replace the one I gave away, and the two I've run with Bunna-N O rings from ACE Hardware run fine, and the rings seem to last a long time. The third is a newer model with beam mounts, and is still new.

Some day I may try Viton O rings, but so far have not had reason to switch.

Bill