ma pit bike jumps out off gear can any one help me?

[danielelphinstone]

hi av got a pit bike 140 cc and it keeps jumping out off gear can any one help me

 

[topchief]

Most common cause for this is worn selector forks.

 

[desert camel]

faulty selector fork/drum..may be worn.

 

[pro08]

clutch worn or gear box.