used to use the 6 speed 125s based motor in bucket racing [hotted to the hilt] & had/have blown up bits everywhere from days gone by!! but a few years ago i put a 200 top end on an old 125 bucket bottom end. Had to shorten the cylinder & had a cam ground to [by memory] a Ford RS2000 grind but spread the lobes a bit to get the valves to clear each other on overlap so as not to have to cut the seats way back!!. This was our best 125 bucket cam back in the day and was copied by a few. My mate worked [part owned] a camshaft shop--experimental days & like i said--monumental blow ups coz i was [still am] too stingy to buy new valves an conrods [slow learner]. Anyway, umm, where was i. So this 125/200 went into an XL185 frame, ridden up the road & parked for years till last weekend & got it going [stale fuel etc] to chase the kids around a slippery grassy small track. Was a bit wary for a few laps [maiden voyage etc] but it fair howls & was sooo much fun to ride. Light weight [minimal stuff on it--bare essentials], turns on a dime, pulls wheelies, & can clutch it out of a corner like a modern YZF. Short stroke & big cam makes it a little rever & i just remembered i have a new 'wiseco' 12 to 1 piston kit somewhere. I feel a plan coming on. Love those little motors.