2003 kfx400 backfire

[kawasaki rider]

hello i just bought a 2003 kfx400 last night, i was riding around alot today and its night time now and my dad said that the exhaust is shooting out flames alot. i have a pro circuit ti-4 slip on, uni air filters. and the guy that i bought it from said that he changed the gearing. is there any reason for me to wory about this? will the quad haev a seized engine or will the tranny blow from this?

thanks

[Demon Rider]

Hey; If your gettin flame coming out the pipe you should be able to hear the bike as it backfires as well. Also gearing should have no effect on this at all.
I can't see you blowing your engine or tranny from this either, providing of course there are no other symptoms. In the mean time I would think your fuel/air mixture goin into your cylinder is too rich causing unburnt fuel to get out into the exhuast and is ignited there by hot exhuast gases giving you that flame your dad is seeing.