I have a 1986 sachs carrier I.
When I start the moped up it has excellent acceleration but right around 25 mph, the engine starts to shake. This continues until its max speed of 30 mph is obtained. The bike will act like this until I shut if off, walk away for a moment and then start it back up. After that, the bike will have less acceleration but won't shake and gets a top speed of 34-35 mph. Any ideas why this would happen?