I have 2 48cc 2 cycle and one 66 CC , I have rode both of the 48cc bikes for hours at a time at 25 to 26 mph with no problems. Most kits come jetted rich which helps keep the temperature down, if you have changed the jetting and are a little lean the engine will heat up. I try to jet a little on the rich side, mine will 4-stroke a little till it warms to full operating temp. Just pay attention to the felt heat from the engine and you probably will be OK.