Fzr 600 got killer spark pulls fuel valves in check wont start just turns over once in a while it while spit through the carbs or backfire through pipe few and far between carbs are clean plugs are new fuel pumps kicking what the@#%*!

This is not the news you probably want to hear but backfiring thru the carbs when you have good spark can be one of 2 things... either the valves are sticking / not closing properly due to carbon or the cam timing has shifted from the original position.

It would be best to do a compression test. You should have a minimum of 100 PSIG for an engine with major problems and up to 150 for a healthy engine. If you can not get 100 PSIG then it will be time for some serious engine service.

There is a possibility of the kill switch wire in the handle bar grip grounding under the grip to the handlebar but, since you said you have killer spark I doubt this is your problem.

Thanks for using FixYa.

Kelly

Backfiring through the carb can be ignition timing too advanced,air leaks on exhaust system which weakons the mixture,

Sounds like you have a vacumn leak or it is out of time. Be certain the fuel is drained completely out and refreshed with new fuel.