That's a good question. Although I don't have a 420 Rancher service manual, I do have a lot of other manuals and I've looked at them all and can't find anything about the clutch engagement RPM in any of them. You may be able to call a Honda dealer service dept. and they might be able to tell you. Sorry I couldn't be of any help.does any one know the engagement rpm on a stock rancher clutch ?