Backfire, please help
 

I have a 97' CBR F3 600, it was recently sent for repairs because my motor and carbs were put of sync. The bike has been running well for a few weeks now since the repairs were completed, however this morning I found that it would not start and even began backfiring. Does anyone have a suggestion of what could be causing the issue or advice on how to fix it?

Hi and welcome to the forum. Can you provide any history on the bike? Past maintenance other than what you've mentioned about the carbs?