Howdy Fisher. Sorry for not getting back to this b4 now. I lost the thread. When drive chains are new, they stretch a good bit so while breaking in a new chain, I use a tensioner. Helps with making install easy and having a safe and right lengthened drive chain. Many folks think I am wrong on this but after that, I do away with them. Really, most folks think this is wrong so take it with a grain of salt.
I looked at many web pages searching for that #, but found nothing. Could use a tach to figure out the RPM. I have never done that but should work great. Thinking about it, would give you truer numbers then what the manufacture might tell you. Not saying they would lie, but with a used engine, might differ. Even with new, I dunno how close it would be. Cool thing to study, thanks! There is a thread on tachs. here is one that was mentioned;
Digital Hour Meter and Tachometer | Hour Meters + Gauges | Northern Tool + Equipment