Chainsaw Repair

Yes on the clamshells.

Stihl MS250 Chinese clone ($32.50 w free ship) would fit the bill. You would need a hub, electronic ignition ($50), and a intake manifold/carb.  Could even use a MS 250 muffler especially if you get the two piece one that comes apart so you can open it up some. Saw off the PTO side of the crank and your prop hub goes on the flywheel end