2001 Honda foreman 450 backfire problem

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toddspolaris

Member
Wow, sounds like I just shot the neighbor, Doesn't matter warm or cold, can be riding around in 2nd or 3rd gear and let off the throttle and bang, backfires extremely loud. Checked the valves and adjusted, cleaned air filter and even removed carb to inspect. I do notice there is a small exhaust leak where the muffler slides onto the pipe, do you think this leak could effect the backfire problem? Or what else to look for? Any thoughts? Thanks Todd
 
Z

zltim

Member
Have you checked the rubber intake manifold, between the carb and motor. My 1990 300 went bad and it didn't run very well with the extra air leaking.

Just a suggestion. I don't know if the 450 has that part but it probably does.
 
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anonomoose

New member
Backfire is caused by raw un-burned vaporized gas that gets thru the machine to the muffler where some oxgen mixes with and makes the explosion you are hearing. That does mean that oxygen is entering the exhaust somewhere...and seems you have already found that spot. Choke off the oxygen and no more explosion. I would try and figure out why so much unburned fuel is getting passed thru the motor. Something isn't being metered correctly.... While rich is recommended, too rich can waste gas too.

Backfires are not caused by leaks in front of the flow of fuel TO the engine...only after it is exhausted in the exhaust pipe or most likely in the muffler where it accumulates and the back pressure from droppin off the flipper causes the oxygen to draw back into the muffler creating the perfect conditon for the explosion.

Class dismissed.
 
uncle_ed

uncle_ed

Active member
I have a 99 Foreman 450 that does the same thing. It runs great all the time and have no other problems with it. The only time that I have this issue is when I run the rpms up high for a bit and then let off the gas and let the motor slow down the quad for a bit and then KAPOW! I just try to avoid that scenario but would like to know myself if there is a remedy to eliminate the explosion. From what I have read elsewhere it is a common problem with several Hondas of that size and vintage. I dont worry about it too much as it is infrequent and only happens on occasion under the mentioned load above.
 
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landoman

New member
Dad has the same issue on the same ATV. He could care less about it even as I razzed him pretty bad about it as we ride polaris ATV's. He has over 10,000 miles on that ATV. He has rebuilt the motor 2x not because it was broken, but more because he was bored and thought it should be done.... Must be nice to be retired.
 
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