Ok so went to start my bike and it keeps backfiring. Won't start. New plugs last year, new air filter a couple weeks ago (started up after i put it back together) gas was put in fresh on new years eve with Sea Foam. It turns over and wants to start (it seems like it's sparking) then all of a sudden BOOM... back fires...

 

Have you tried taking the vacuum pipe from the fuel tap off the carb and sucking on it for 15 seconds or so? It sounds as though your carbs may have run dry.
Give that a go and if you get no joy come back to us.

 

Crabs or FI and how much throttle are you giving it? The battery may have enough to crank it over but if it is not charged enough, the spark will be to weak and it could back fire after a miss fire.

 

Good point Tim. Batteries can be the make or break on these bikes.

 

My guess is fouled plugs. It doesn't take much at all to foul them,.. cold temp outside or low battery that cranks the bike too slow are the most common.

Did the bike crank over slowly at all?

If its backfiring, as in through the carbs, it could be a timing issue. But if its out the exhaust, which it sounds like it is, its a fuel spark issue. What is probably happening, is the sparkplugs are not firing strong enough due to being fouled, then the exhaust system fills up with raw gas, then you get one that sparks enough and you get the boom of all of the gas being igninted.

If it were me, Id change the plugs again. Make sure your battery is fully charged and it should fire right up. Even if you dry out the old plugs, they will probably not work correctly. Just replace them.

this is of course based only on the information given. but based on that.... that would be my next step.