Re: 75 to 90
People look at engine specs and see that the displacement is the same and assume that its bigger jets or some little tweak that makes the next larger size engine. In the case of two strokes, porting, exhaust tuners, carbs, and timing can make the difference. In four strokes its camshaft profiles, carbs/fuel injection systems, exhaust tuning and ignition timing. From the manufacturers perspective its inexpensive to build the engine. From the consumers standpoint its generally very expensive.
