Last weekend at the airfield i was flying my YS 110 Fz powered Mustang. the flight seemed completely normal and the sound was just as normal. After i landed i noticed that there were small metal particles in the oil on the wing. I showed this to some of the YS experts at my airfield and they said that i blew a bearing. So i ended missing 3 balls in the rear bearing, so it was replaced. Now i have the engine completely assembled with out the back plate and when i try to turn over the engine, it turns over just fine, but then put on the backplate and carburator the engine only turns over about half a turn then comes to a hard stop. Is the a problem with the backplate or the what? comments please.

Does the disk valve on the back plate turn freely?

yes

First guess is that you have not aligned the back plate with the crankshaft properly,
and looking at the pictures of the disc valve it looks heavly scored, if you pulled the assembly apart
the back plate will have the grand canyon embedded in it.
It could also be binding when it is assembled.
The disc valve assembly may still be repairable, but only by someone who knows what they are doing, or just replace it.


XMANS
YS Down Under

That could happened beacause the disc bolt was probably overtightened. That bolt does not have the normal torque like on regular bolts in the engine.

Regards

The same discussion is in Glow Engines.