Just bought my bike one week ago and it backfires constantly and I have to keep it idoling on high or it dies whenever I come to a stop. The past owner had the bike and when he got it, it had custom pipes and a custom air filter already on it, and it ran good for a year and then he parked it for about 4 or 5 months and when he went to start it, it started backfiring and that's how I bought it already backfiring. what could I use to stop the backfiring? Can I put a mixture of something in with the gas to see if that works first? or should I start off by having the double carburetors cleaned? If the first two things I said don't work should I just have them rebuilt by a mechanic? Also if I start off by putting a mixture of something in the gas what type of mixture should that be? and where could I get it from? Please advise need help. Thank you.