I have had good luck freeing 'stuck' ( within reason ) Engines, but, soaking the Piston Tops and Rings as mentioned above, with ATF and Acetone or AFT and Diesel...let them soak a few days.
Any visible Rust in what can be seen of the Cylinder Bores I clean off with an Electric Drill with a Wire Brushchucked u in it.
Then, with a large Screw Driver or short Crow Bar, with the bottom Cover of the Fly Wheel off...I pry in the Teeth of the Flywheel, from the side, just to get a little movement...some back-and-forth movement is fine also.
Soon as I get a little movement, I pry to get it moved several inches, and maybe several more inches...and then have a peek in the Cylinder Bores.
Wire Brush on an electric drill, to clean the Bores as far as possible in this position...then, turn some more till two of the Pistons are as low as possible...clean the two lowest Piston's Cylinder Walls then, and repeat till all six are done.
I used a Dremel with a little Wire Wheel on it, last time as well...
Once all are clean, Lube well and crank it over a few times to get everything slick again.
Last edited by Thriftmaster_Phi; 07/30/2014 2:42 AM.