Hi run a kr250 in pre 89 and having a few crank problems . kr is a rotary and reed valve inline twin,vertically split crankcases, with two cranks driving onto the primary gear .My main issue is it has die cast ally inserts for the main bearings that are cast into the crankcases and are working loose and sometimes cracking,mainly on the flywheel side of the engine and the main shaft is wearing inside the bearing. Wanting to know if any of your bucket engines have same type of insert and issue .The fault maybe in the kr design as it has very heavy cranks 2724grams each with thick webs and long crank pins then out side the crankcase the front has altenator 1290grams the rear a flywheel 1482grams the rear flywheel is smaller diameter the alt has most of the weight on the outside ring, both run in oil from the gearbox casing. The drive side has a gear hub with a three lobe cam and matching internal splined cam held together in tension with a stack of cupped washers like a mini version of what the old pom bikes had.The cams are not symetrical and can rock up to 15 or more degrees but the shim stack has little compression height so it cannot rotate,each drive onto a primary made of two gears on a rubber cush hub .There is no control of side float of the cranks apart from the main bearing spacing and the drive gear floats on the main shaft spline and has a outrigger bearing in the primary case .I think the last of them (only three year model life) did have a thread on the shaft and a nut to hold it .Have added some pics thanks
Bookmarks