Hi all. i have an 05 wr450. Bike has drd pipe no ais. The bike has started to backfire when using the Estart. About every5 rotation the bike backfires. it will idle fine once it starts. It also need to hotstart to fire now. I don't remember it needing it before the back fire started. I changed the header gasket thinking it was sucking air but it did not fix the problem.