well its on ,pulled engine and split cases tonight also picked up an old 230 cyl,head and cover (withcomp release). head is basically the same with seats cut for 28/ 32 valves instead of 26/30. ports appear to be close. cylinder is roughly around 5.5mm taller and cover has built in mech compression release lever ( cable operated I suppose).Old engines use stud and klx uses bolts on cyl and head. there are about 6 or so engines that share similarities with the klx 125, so possibilities are plenty.main bearings are the same up to the 230 and poss even some of the 250s. I found a guy who has alot of this old stuff and was diggin and comparing all night(except for dr 200). rod has plenty of clerance inside lower end for plenty of additional stroke,crank throws are the only concern with only about .080'' clearance to 5th gear and about .200'' to 4th. plans were to look into a dr 200 crank yielding about 10mm more stroke and larger wrist pin, but dont know if the throws are larger and if so by how much. stock 125 throws are 4.325'' if anyone knows throw diameters on a 200,230 or whatever else may fit in to these cases or have any other ideas I would appreciate the help. plans are to build something at least 250cc with lots of head work,custom exhaust,cam,carb and whatever it takes to make it an all out performer. my son plans to ride it with the 250 class just to be different and have a father son project as well.