4 stroke.

[Diy89]

If I were doing it, i would like the converted stringtrimmer i did for a rc boat.
Stick the jug in the lathe, and cut off the cooling fins. Then cut clockwork slots in what remained. Use orings for seals in top and bottom of a close fit barrel. Water in on bottom, out on top.
That said, your not going to get that jug off (on the saito), so making a fixture and using a RT or hand cut it with a dremel.

 

[Speedy]

I actually think making a fixture wouldnt be to bad. but I noticed that the push rods for the rockers are very close to the cylinder.
cylinder to fit into the bore and screw onto the 4 base bots. then chuck into the lathe.
clearance is the issue and it might be harder then I originally thought for a liquid sleeve.

right now I am trying to figure out how to pull the prop hub.
not sure if I can use a small engine puller for this job or not.