Small Engines (Lawn Mowers, etc.): Honda TRX400EX, gas vapors, yamaha wolverine

Question
Hi, I have a honda 400ex, I just put a full system aftermarket exhaust and aftermarket air filter on it. The process of jetting the carb has been quite frustrating, I think I have it where it needs to be, but it still backfires every now and then. it only happens when i rev or ride and let off the gas. I'm just wondering what causes it and if there is a fix for it?

Answer
Hello Andrew:

Usually the Backfire is Caused by Unburnt Gas Vapors in the Exhaust Manifold being Ignited by the Hot Exhaust Gas Vapors. The Exhaust is Hotter when you Release the Throttle After High Revs. The Aftermarket Exhaust System May be Trapping these Gasses and Not Venting them Properly. I have  350 Yamaha Wolverine and have the Same Problem After Modifying the Exhaust System. I have Tried Everything to Eliminate this and Still have an Occasional Backfire. Change the Muffler to a Flow Master. The Every Now and then Tells me the Exhaust System is Not Exhausting Properly and Allowing Unburnt Gas Vapor to Build in the Manifold. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

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Respectfully

John