My brother Doug and I  tried a YS 63 a few years ago, but
we just couldn't get it calmed down enough to be an effective
stunt motor. The motor has gobs of power, but we were unable
to harness it for stunt use.

Later, Steve

Anybody flying a YS motor??

Windy gave up on it and went with the Saito's and the O.S. Max. There is a video of him tilting the motor all the way back while it is on the test stand and it never hiccupped once,(it's supercharged). Of the half a dozen RC guys I personally talked to who owned it, ALL of them said it gave them trouble. Three of those guys quit using it and went to two Saito's, and one O.S. max. The last O.S. max guy quit that, and went to Saito.

I hand started a couple of YS 53's some time ago. They are not like the Saito's with it's normal "snappy" 2 stroke type compression. They have a strange soft feel to them and, at least for me, are VERY HARD to hand start. No RC guy I knew of hand started any of them.

The YS63 can pretty much go up against anything we fly, on a power basis.