Hello

I've got a ys-63 wich runs great but there is something that I'm not completly satified with. When the engine spends some time in idle and I hit full throttle it takes about 5-7 seconds to reach full power. I rarely take it to idle during flight since the airplane that I have it in needs speed (I probably land at 1/4 throttle) also when it reaches full power it will go as high as 11700 and then go down to 10900. The engine won't quit or sputter it only takes too long to accelarate. Can someone tell me if it's the low end needle or the regulator or what? I'm flying with powermaster saito/ys 20/20 and a 13 X 6 APC. Everything else this engine runs great and has lots of power.

I found some great directions for tuning YS engines. When in doubt, this is what I resort to (requires a tachometer):

At WOT, set high needle for max RPM, then back off a few hundred RPM with high speed needle.

Next, drop throttle so engine is at EXACTLY 4000 RPM, and watch what happens for the next 10-15 seconds. If RPM increases, regulator is lean and needs to be made rich. If RPM decreases, regulator is too rich and needs to be leaned.

Last, drop throttle to 2000 RMP and hold, see what happens over next 10-15 seconds. If RPM increase, low mixture is lean, needs to be made rich. If RPM decrease, low end is rich and needs to be leaned.

I'm pretty new at this YS thing but sounds to me like some things are rich on your engine. Best to check everything as it is a 3 part system and all need to be working together properly.

I just want to add, make your adjustments very small. 1/8 or even 1/16 of a turn isn't too little.
Paul