Clutch bevel won’t stay on? + gas bike frame question

[Redm777]

So I opened up my bike clutch to only find out the bevel gear will not stay in place and it can pop out. How would I secure it and would I need a new clutch

Also what is the seat post size for the gas bike frame? 1 inch does not fit also a mtb seat post doesnt fit either.

 

[ImpulseRocket]

The clutch gear rides on the thin bearing in the center. It's just a slip fit/light press fit over the bearing in the center. If it has excessive play on said bearing you can buy another one but there is nothing that holds it in place other than being sandwiched between the front and rear plates and spring pressure. That is what allows the engine to turn without engaging the sprockets when you pull the clutch in - the gear spins freely.