I just purchased a used 53 and new 63. Both run great. My issue is with both engines but because I am flying the .63 now this is the one I will discuss. I own OS, Magnums, Saitos but these are my first YS engines.

Facts:

Fuel - WildCat 20/20
"F" plug
Laterally mounted on a Funtana
APC 13X6 prop (broke my 13X4W)
Good smoke trail throughout throttle range.

This engine runs perfect at all throttle setting. Response from idle to full open is fair, but I believe could be better. Seems a bit slow to me. But maybe it is just new.

The only situation that concerns me is a rattle at 1/2 throttle. Almost like predetonation. Is this a charactoristic of YS or is it something else I need to change. I have less than a gallon through it. It may be there at full throttle, but I dont hear it much. I'll check the rpms tonight and let you know what that is.

Perhaps too much prop?