Thanks for the advice Bax. I am planning to “tie it up” in the back yard and check the top needle setting with a tachometer. I had a similar problem with my other ringed engine an OS50SX and when I flew it last Sunday I could not help noticing how smooth it runs (it’s a year old now). I hope that the 91FX will go the same way; the only problem is that we got a pattern meet in ten days time.