brute 750 backfiring through carbs

[bt650i]

Just rebuilt 750 engine, was bought in pieces, have verified camshaft timing a million times, any suggestions as to why it might be backfiring through the carbs??Thanks in advance....

 

[lucm]

ck this site out and you will get your answer.....

 

[Garryese]

If you are trying to run it up without the air filter or airbox fully assembled than it will cough back through the carbs. If the airbox is assembled, make sure the airbox is seals to the carbs.