I need help figuring out how this engine works and what could be wrong with it.
This bike worked great for like two weeks before it started struggling, I'll explain at the bottom.
So how the engine starts: the bike has a clutch on the left handed side, and you need to pull it back to use the pedals, and when you pedal to about 10 mph or higher you can drop the clutch and the engine normally would start, and then you can use the throttle on the right handed side to control the speed, both sides have brakes.
It has a small copper colored bar on the right handed side that when pulled up helps the engine start cold, and has a fuel control (sorry for the bad discrimination I'm going off what I've been told by my stepdad who bought it used and gave it to me.)
The problem is: after reaching a speed (it changed over the course of a few days, going from 25-20-18- and just kept getting lower). But when you hit that speed the bike would stutter and slowly stop taking throttle and start slowing down, but it was still getting throttle? Like you pull the clutch that should make the engine stop pushing the bike forward, and it makes the sound that happens when you pull the throttle.
It even sped up a bit today, it went from 19 to 20 mph before going back down.
Conclusion: I don't know what's wrong with it, my stepdad has no clue what's wrong with it, the only thing that's happened was it was knocked over a week ago and that started the problems but we can't find anything visually wrong with it.
Sorry for the long message, your rules said no low effort posts and I wanted to give all the information I know. Someone please help.