Originally Posted by Sydneysider
the 80cc would accelerate quicker and reach the higher end speed because of the torque and power.. my main point here is the highest rpm before the things go bang taking into consideration that all components are pretty much identical in these motors except the bore.
Exactly. In fact the 50cc will actually rev higher than the 80cc with a light load.
The issue is torque. My 50cc bikes, unlike the 80cc, just don't have enough to get up there with that small sprocket. Maybe the slant 50s do.