I have been using this little book and telling folks about it for years. I bought it years ago when I sent in an OS .70 for service to tower. They told me they would test run it and let me know what was wrong before they did anything to it. I was sure it was the needle valve, I had flown the plane through a tree and the engine wouldn't run after that. Tower took it apart, let me know it was run lean, had bent parts and was going to cost me a couple bucks less then a new engine to have it repaired. I had them send it back to me, it was in the box but taken apart. Bought the book, assembled the engine and it still wasn't running correctly. Replaced the needle valv assembly and ran the engine inverted in a IMAA plane for three years without a dead stick. Last engine I ever sent in for repairs.
The book may still be printed?? A GUIDE TO OS 4 STROKES By Graham C. Rice and sold through the RCM Anthology Library?? It used to be sold in most hobby shops for just a couple bucks. You don't see a lot of Gudgeon Pins in newer engines but other then that it's still everything you need to know about most 4 strokes.