Have a 2003 kfx 400 decided to go for a ride and after 10 minutes it started to bog down after giving it gas.It starts right up and idles like it was new.It bogs down after reving it up will run all day at idle.The only warning i got was it did backfire a few weeks back and conked out drove it back to the garage and parked it.What could this possible be.Spark plug? Cloged carb? or electronics. Could use some help .