I reconditioned an Aprilia Rs250 engine for a friend so took some pics in the process. Lovely engines, some small issues on cylinder castings, the LH reed valve blocks the rear intake port, RH crank case needs some remachining blah blah blah and the usual stuff.
Port heights and blowdown time are on steroids! Very nice intake and everything coupled with a good pair of adequate reed valves but I don't like the carbs though.
LH and central crankshaft bearings are 83464A-9TC3 (with dowel pin) and RH bearing is 83580-9C3 (dowel pin & groove).
Some oil keeps the washers in place and ease piston installation. I didn't used the expanders below the lower piston rings.
Duh... trying to find a second good pair of exhaust valves. I wouldn't describe the person that designed this exhaust valve as a minimalist. LOL