mechanical issue i have on the kymco 300 maxxer

[amithadad]

I recently bought from someone a kymco 300 maxxer with problems he did not want to fix. The ATV has some problems:
The ATV goes to reverse while the lever was on neutral
When I shift from drive to neutral or reverse the ATV shuts off sometimes
When I touch the gas in neutral the engine revs with an unhealthy sound (the only way I can describe it is that it sounds like there is a lug nut shaking in the engine)
Sometimes it just doesn't want to start and I need to play with the gears in order to get it going

So from all this I think the problem is in the gearbox but I do not quite understand it so I do not know what the problem is exactly
Do you have any idea what causes this?
(sorry if I have bad English it's my second language and I haven't mastered it yet)

[airshot]

Sounds like it might be a linkage adjustment.   There are safety switches built into the gearbox that keep the machine from starting in gear unless brake is depressed, that along with not getting into gear without grinding sound like the shift linkage is way out.  Get yourself a service manual and all the adjustments wil be shown in there along with all specification you will need

[amithadad]

ill give it a try. thanks!