Hi everyone, just looking for a little advice or direction with an issue. Just picked up a 1987 CH150 that was in good condition and only about 2000 miles on it. I am down to about 1 remaining issue that I am trying to sort out.
Scooter starts great, has good acceleration, no stumbling or misfires. It can cruise at 45 mph no problem, and can accelerate up to 50-55 mph without any issues. But, if I try to cruise at 50-55 mph for more than about 30 seconds the engine starts to surge like it is running out of gas. It won't die though if I let it slow down to about 30 mph or so; and then I can re-accelerate back up to 45 mph no problem.
Spark plug, air filter, and gas cap have been replaced. I have tested the fuel petcock, and the vacuum function is working normally. Although I am wondering if the engine isn't providing enough vacuum at high RPM to keep the petcock open; thus the reason why it doesn't start to surge for several seconds at that speed. Also I have verified that the fuel screen appears clear, and has no debris restricting flow.
I appreciate anyone's thoughts on what might be causing this. To me it feels like a fuel issue, and the petcock/vacuum seems like a possibility. Other than this issue, the scooter runs great.