I haven`t started my bike for a month. So today I started it up and let it idle with choke on until it was warmed up. When I gave some gas and let of the throttle it was backfireing like hell, flames coming out of the exhaust. What could the reason be? It has had a minimum backfire before, but rarely. Also it is a lot cooler around here then a month ago. Could in be a jetting issue or something else? PS. It makes "buff" second after shut down. Sometimes even a little flame out of the exhaust.