Hi Dave,

I have both a 63FZ and the 63S. The 63S is a real beauty - runs and tunes easily right out of the box. Both engines are new.

Unfortunately, I've been having problems getting the 63FZ to run consistently.

I have managed to tune for max rpm and richen out the main needle by 2-4 clicks for flight. It has a decent transition from idle to WOT and maintain a pretty solid idle.

The problem is that it doesn't maintain this setting and seems to lean out(?) in flight. It would start to loose power and somewhat regain composure after I back the throttle to half, but would usually be forced to land soon after.

I started with a 12.5 x 6 prop and have since changed to a lower loading prop (12 x 5) to help with any temperature related issues. Problem still persists. Fuel is Cool Power 15% Heli (tried Cool Power 30% Heli, not much improvement) and OS F plug. Max rpm with the 12 x 5 is 11,200.

Lately, the engine has been having some problems transistioning from idle to WOT - sometimes taking 10 secs or so to get to WOT. I have tried leaning and richening the regulator to no avail.

I have replaced the diaphram - no change in behaviour.

I would appreciate any help you can offer.

TIA,

Chen