My XT250 - 2Y motor only gets 105 Km/ph on downhill. On a flat 90 is about max. Uphill about 75 km/ph. I had new cam, valves, piston and rings, filter and service. 121 km/ph was only when new. 28 years is a lot of wear. Mechanic said if I want it to go faster, it will fall apart, so 90 km/ph is not so bad in the long run.