Backfire

[pmd31421]

Hi had my XS650B running at the weekend . Took it for a short run and it was backfiring .....very loudly from the left hand side . What should i check out first ?
Pete

 

[jaredhodge]

Try syncing your carbs

 

[bergoff]

Sync and clean the carbs

 

[nj1639]

How's your exhaust system?