Frozen motor

[AwL]

Hi - New to Forum since i just picked up an '83 FT500 for winter project yesterday.
It has sat since 2010, some period of that outside, and no information on why it was parked.
Engine frozen, Hoping just rings rusted onto cylinder. 
Haven't taken head off yet but did put some of the supposedly ultimate free-er upper mix of ATF and acetone into the cylinder to soak.
Any other insights into freeing up a motor?   Thanks, Al

[murdo]

Hi Al and welcome.
Try putting the bike into top gear on the centre stand and rock the back wheel back and forth after a couple of days with the mix in the cylinder. As you turn the wheel and the backlash of the gears take up it gives the crank a little shock. Doing this both back and forward over a couple of days will usually free stuck rings.
If no good then you may have to rebuild the engine.

[AwL]

Thanks Murdo - your suggestion plus mix of ATF/acetone in cylinder free'd up the piston.
Valves stuck but was able to rotate enough to remove head.
Cylinder wall corroded pretty bad but doesn't look live corrosion is below the piston.
Project secuity!   Al

[murdo]

Bad news then.
There seem to be plenty of aftermarket oversize pistons available for the FT's, so a rebore and some new bits and you will be away.