Yamaha RT1 Engine - New Piston, Rings, and Bore

Engine from a Yamaha RT1 (an early '70's 2-stroke enduro dirt bike). The piston, rings and cylinder bore are new. Before I got this engine, the previous owner bored out the cylinder, honed it and installed a new 1/2 over piston and rings. The engine has not been run since these parts were installed. This may be because the crank doesn't turn. It's possible the crank was assembled wrong, or there is some other issue, and that's why the engine's new piston was never put into service. I don't really know. The transmission turns freely and shifts through the gears with no issue. See pictures for further details. Shipping weight - 80 lbs.

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Yamaha RT1 Engine
Yamaha RT1 Engine - Right Side - missing automatic oiler and the cover.
Front view, showing exhaust port. Piston can be seen inside.
Left side view - flywheel cover and drive sprocket cover are missing.
Left rear side. The transmission shifts and turns freely. The crank, however, does not turn.
Rear view - showing intake port with piston visible.
The piston and rings are brand new. The engine was never run with these parts. Marks seen on the piston in the picture are due to grease smudges.
Front view of piston. The rings and piston show no issues. The engine was assembled, but as far as I can tell, never even turned over. This may be related to fact that the crank doesn't turn. Perhaps the previous owner assembled the low end incorrectly and just left it at that.
The piston is a 1/2 over piston (shown by the 50 on the crown). The cylinder was bored and a new piston and rings installed, but the engine was never used. Some dirt and crap has fallen into the crank area (through the open ports). The engine needs to be taken apart and cleaned. The transmission oil looked reasonably clean, though.
Showing cylinder walls from top view. Note hone marks. The piston makes a tight fit. I'm pretty sure the cylinder was bored to the 1/2 over size and then honed for this new piston, not just a new piston slapped in a worn out cylinder bore.
Another view of cylinder walls, showing exhaust side. Smudges are grease marks. The cylinder bore is new and clean otherwise. A used copper head gasket is included, but not shown.
Cylinder bore from bottom side, looking at exhaust side of cylinder. Used base gasket is present, but broken (half on cylinder, half on engine case). So, it can be used as a pattern to make a new gasket by hand.
Serial Number: RT1-128189 (sorry about the blurry picture)