Ok - I have a brand new K&B .20 that as far as I am aware, has never been run (looks new in every regard). Normally, I like to perform some break-in engine runs on my test stand for new (or new to me) engines before considering it for installation onto a plane. However, I've run into a serious problem - whenever I tighten the prop nut, the crankshaft counterweight gets pulled so tightly against the inside of the case, that it will no longer rotate. Loosening the nut to a point where the assembly will rotate only makes the prop slip. There's some discernable crankshaft end play that I hadn't noticed before - is there a fix for this such as placing a thrust washer on the inside face of the counterweight? Anyone else ever had this issue?