Motorized bicycle rear tire locked up

[ayo2001]

Ok so i have a 66/80cc engine bicycle, and right now im trying to figure out why the rear wheel is locking up when the clutch is out, it moves freely with the clutch in but when i ride on it and get up to speed, ill let go of the clutch to start to engine but the rear wheel locks up and the engine doesn't even start at all, does anybody have any ideas what the problem might be? thanks in advanced.

 

[mikedabomb]

I think the engine is seized/locked up. If you ran it too hard and it mysteriously died, you overheated it and the piston and rings might have gotten destroyed and pinched somewhere, making the engine unable to cycle. I'd pull the plug to relieve any compression and try to turn the engine crank. If you can't turn the crank with zero compression, something went wrong and something is holding something where something should be able to move free.

 

[KCvale]

I'd start with your drive chain caught on the case or sprocket behind the back left engine cover where the clutch arm is.

Pull that cover off and look.
If the cover has grind marks from the chain in the front, grind it out bigger or cut that edge off so the chain can pass.

With the plug out you can roll it even with the clutch not hooked up.