I have a 2009 SportCity One 125 and I am having problems with the scooter losing power at speeds 35mph. For example, when I hold the throttle steady at 35mph the scooter will run fine for a quarter of a mile then start to lose power like it is running out of gas. If I let off the throttle and get back on it a few seconds later the scooter will run fine for another quarter mile, if i keep on the throttle the scooter will stall out and take a while to start.
The things that I have checked so far all looked good. I checked (and cleaned) the carb, fuel lines, and fuel tank, all were clean, the vaccum lines were all in tact, the petcock was flowing fine, replaced the spark plug, and ran the scooter with the fuel cap loose to check for vapor lock. None of these things seemed to solve the problem. The bike seems to lose vaccum at higher rpm when checking it at the petcock. The valves are also within tolerance. Any suggestions would be greatly appreciated.