You are most likely going to have to take the side cover off.
I would start by draining the oil and taking the clutch off and check for debris (if you have an impact wrench you can use it to remove the centre nut of the clutch basket if you are careful)
It looks like on the 2strokes this is also the side for the water pump so if you are taking the entire side cover off it will probably need to be drained. ( you can take just the clutch plate off without doing this but to fix it you will need to take the side cover off)
I would get new gaskets and seals just in case they are worn or swollen. ( i got mine from Beta UK website last time )
Once you have the side case off look for any debris in the bottom on the case and inspect the kick start mechanism and clutch basket to see what is broken.
Beta UK website does have explosions diagrams of everything you need under the part finder if you need to check anything.
Take what I said with a grain of salt as I normally work on a 4T which is slightly different