EC300 engine/transmission stuck after oil change

[JBK]

Hi! The title pretty much tells the problem. But I had my bike idling right before changing the oil but now after 14 hours from changing the oil, the engine is stuck. I think I put like 50-100ml too much oil in but that shouldn't cause the whole tranny to get blocked? Should I start from taking the clutch cover off and rebuilding the kickstarter or something? Or what?
I only have 2 days to fix this so all help is very appreciated.

In advance, thanks for the help

[gasgasman]

I would pull the clutch side inner cover off and look at the shift selector.

Could also be the crank stuffer bolts came loose.

What year bike?

[JBK]

The shift selector works also and all the gears go in. Could the crank really be the problem? The bike ran completely normally right before changing the oil.

And the bike is a 2013 model

[Doc Brown]

Any news?

[Gasser Nate]

Take the rotor side cover off and see if the crank spins. I can almost guarantee it those stupid crank stuffer bolts. I have repaired about 10 of them myself. Most painful part is the crank needs to be split to replace the smashed plastic stuffers.