Stuck engine backplate

[KenChoo]

Hi Guys,

For some reason, the backplate on my OS91 CSpec PS is stuck to the crankcase! I can only twist it side to side (even then it's awfully difficult to do). I need to remove it to use the crankshaft lock to tighten the fan. Any ideas on why it's stuck (I'm curious) and how I can get it out?

Thanks,
Ken

[wjvail]

Stuck Huuu... I've never heard of that.

Are you the first owner?

How old is the engine? Any damage to the engine (bearings, piston crank)? Has it been crashed? Did you ever LockTite the backplate screws on?

Did it ever run with the fan loose? That could have caused the crank to move backward and rub on the backplate. That might have allowed aluminum grit to get between the backplate and case making it hard to move.

I might guess that it's got some sealant (RTV or Air-Seal) on it, it's bent in some way, or it got some thread lock on it the last time it was put together. Again, just guessing.

Did you try using some heat? That will soften many glue's and might free things up. As a last resort I might try grabbing the backplate in a soft jaw vice and using force.

It should just slip off. In some engines the Piston will key into the backplate when at BDC making it impossible to remove the backplate unless you move the piston up. This isn't one of those engines.

Without more information, I'm just grasping at straws. Let us know what you find.

Bill Vail

[RC-Bearings]

Try heating the engine to about 250F. This will allow the crankcase to expand a little relative to the backplate.