I would guess its still the plugs. you probably have one or two that are not fouled, but the other ones are fouled so it wont start but will fire. Dont be suprised if it backfires too.

Be careful jumping the battery too. If you put too much charge into, you can fry the battery or electrical components of your bike. Its not like a car that you can hook up a big charger.

 

And personally I never believed anything about plugs being fouled and always told myslef couldn't possibly be fouled plugs until my 900rr wouldn't start, I dropped four new plugs in and viola fired right up