I can get just over 33mph out of the 32cc I ride - and it seems to like flat out and not have any problems doing 20 miles at that speed..

However under 20mph is a different proposition - it sounds rough and uneven as if it doesnt like that speed and my 'mechanical ear' doesnt like the sound it makes either..

I think, definately with the commercial engines, that they are designed to run full power for extended periods and for some reason they dont like partial speed running as much...

As long as the petroil mixture and such is correct and the state of the bike/tires/mounts etc is monitored these machines should run wide open all day

Jemma xx