bike running crapy

[shaun]

when i try and ride my bike fast it just revs up and down and backfires. can any one tell me why it would be doing this and how i could fix this?

 

[no_crf50_here]

Check for air leaks after your carby

 

[thump*140]

shaun if you can us a few more details, someone will be able to help..
eg engine size, carby type and size, jetting combination etc....
saying it runs "up and down and backfires" kinda doesnt give us much to work with...