Kawi2strokes.com Forum

There was no 250 race at the 1982 GP of Argentina, though there was a 350 race; Anton Mang also raced a KR350 in the 500 class. To be able to race in the 500 class legally, the KR350 would have to have had its capacity increased by either increasing the bore slightly, or increasing the stroke. The former would have required boring a cylinder block and replating it, plus a set of special pistons made, and slight head work to adapt the combustion chamber to the bigger bore; an 0.5mm increase would have been sufficient. The alternative, increasing the stroke slightly, would have meant making excentric crank pins as was done for Yamaha TR3s and early TZ350s; Yamaha offered such crankpins which increased the TR/TZ's stroke to 55mm, increasing the engine to 354cc and thus legal for the 500 class. Presumably the TR/TZ 354 conversion only required an extra base gasket to be fitted to compensate for the increased stroke. This would probably also have been the case with the KR350.
Mang only raced the KR354(?) in Argentina, even though he could have easily done so in several other GPs as well: Austria had no 250 race either; Spain, Belgium, Yugoslavia and San Marino no 350 race. Just out of interest, does anybody know how the KR's size was increased (bore or stroke, my guess is stroke), and why this was its only race?