I've read up on this issue I'm having with my 3600 mile, 1987 ch150 and found that the cdi can go bad. So, I bought a new one on ebay (chinese clone for around $10 shipped). I put it in and the scooter still goes into these phantom and very random power losses where the engine cuts out and seems to run at 1/2 power. Eventually & and also very randomly, it'll come back to full power. Sometimes it'll stay at 1/2 power for the entire 2-3 mile inner city ride. Other times it'll stutter for 3-10 seconds and come right back to full power. Other times it';; feel like it's threatening to go into the 1/2 power mode but it never does. It sounds and feels like an ignition issue. I say this because it feels & sounds as if while riding, I've shut the kill switch off while keeping the throttle open... like a backwards, light popping but the engine still has 1/2 power and runs. I have lost some top end. I used to be able to jump on the highway and run up to 60mph pretty easy but now I'm struggling to hit 55mph. I removed the carb and cleaned it. It's fine. I currently have no air filter on it. The issue did still happen when I had a K&N pod filter on it. I'm pretty certain it has nothing to do with air filtration. I also adjusted the valves. The only thing I haven't checked it the fuel filter and that's because I changed it 2 years ago. The fuel tank has been por 15'ed so it's clean inside. The gas is fresh and new. I'm at a loss.