63 FZ top end rpm
Hi,
I've just accuired a second hand YS 63 FZ which looks ok (although I think that the bearings are a bit worn). I've adjusted valves and I'm now trying to adjust the engine starting with settings as per manual using an APC 12x7 prop and Cool Power 25 % fuel (which works nicely on my YS 91 AC). I've noticed that top end rmp is somewhat unstable. It will initially reach 10500 but then after a few seconds drop to approximately 9800 rpm. Is this normal and - if not - what could be the cause?