The early YS shortstrokes (pre-1983) had a very tight fit at TDC and required significant ground running before a reliable needle setting could be achieved (sometimes as much as 1 hour). They were higher compressed than any other engine at the time and the ONLY engine I've ever owned which would start WITHOUT a glo igniter (just fuel and compression). You could not reliably start the engine without a glo-igniter, but I had my first 2 'FRs' start without a glo-igniter attached on several occasions. The first time was a BIG surprise, fortunately I had a good grip on the airplane. The YS FR/FS engines were the best short-stroke pattern engines ever made (IMHO).
-Will