31cc Mountain Bike project

[RumblingV8]

If you've welded the flywheel on you've totaled the engine.

Unfortunately, this is the case.
Secondly, why would you remove the fan? Engines are built the way they are built for a reason. If it would run fine without a fan then that's the way the manufacturer would have designed it. I've never seen one of these little air cooled 4-strokes without a fan...

Even if you were an ace welder and you got the timing right, the flywheel is no longer balanced and would vibrate badly, destroy your bearings and work itself loose, probably at high speed, and what follows would not be pretty.

 

[USAbro]

The flywheel should not need welding. It installs with a key and a nut. Epoxying magnets on probably won't work. The flywheel spins at high speed and needs to be balanced. If you've welded the flywheel on you've totaled the engine.

Yeah I did weld it on but that's because the key and nut were stripped off somehow. I hope somehow that guy who gave it to me has another engine like he said he might because now I know what to take off the engine and what to leave on. It's all a learning process.

 

[USAbro]

When I peddle very fast nothing is off balance and the engine turns over fine, but getting the timing right is impossible plus getting it perfectly balanced also. The reason I took it off was because the way I attached the BMX bike peg, the fan wouldn't fit. And I heard it was only used because the engine was inside a plastic casing that needed to be cooled more and the constant flow of driving the bike would cool it fine. Anyways, exposing the magnets to a flame destroyed them. I've never done anything with engines before so it's all a learning process I guess.

Oh, and by the way, it's a 2 stroke engine, not 4.