i've built three of these. i think they're awesome motors.
what i do is lap the heads down till the lip is almost gone, clean the transfer ports up in the case and the jug, get rid of all the casting flash in the intake and exhaust ports, match port the intake and exhaust manifolds, NGK BP7HS plug and 7mm copper-core wire, polish the inside of the carb, change out all the hardware to grade 8 allen head socket caps, adjust the flower nut on the clutch so it pulls with one finger, and i use Opti2 oil at 100:1 from the first tank on, and run it full throttle from the first fire-up. on mine, there's virtually no break-in period, and i run at 40+ all day.
one of my motors lasted at least 2000 miles, till the chain snapped and took out my rear motor mount and put a whole in the case. if it wasn't for that, it'd still be running.
put a new motor on the bike a few days ago, and rode 100 miles today at full throttle, going so fast, that if i posted my speed without proof, no one would believe me...
oh, and i also turn it around backwards.
http://motorbicycling.com/f38/backwards-engine-experiment-1939-colson-13458.html
