I am working on a 1998 Honda Foreman 450es when you let off the gas it backfires really loud and I am having issues figuring it out. I have cleaned the carb. replaced the exhaust gaskets. checked to make sure the vaccum valve on the side of the carb is working. I have read that a lot of people have had this problem (but nobody has a good fix for the problem) is there anything you can do to make it stop, any help would be really appreciated.

 

Turn you air/fuel mixture screw out.

 

TTT

 

Did you clean the air cutoff valve ..

 

Theres no air cut off valve on that carb. Is the exhaust system stock...spark arrestor still in?
The back fire is caused by lean mixtures, so look for air leaks, and even exhaust leaks( even a hole in the muffler will allow the backfire on let off.)
If going out on the mixture screw, doesnt improve the backfire situation, then you might need a bigger pilot jet.
Does pulling on the choke....just before throttle let off....stop the back fire? If it doesnt, then you probably have an exhaust leak. If it does go away, then the idle circuit is too lean.

 

What did you set the air screw to ..?.. Did you clean the air screw ..?..If so was the tip black with carbon..?


Did you clean the air cutoff valve I believe that is what you mean by " the vaccum valve on the side of the carb" make sure it is clean and the hose is in good shape..

If it is good try opening the air screw about 1/4-3/8 turn ..

 

my 300ex backfires like its job on decel

but it TEARS it up when i hit the gas

lean is meannn

 

<div class="FTQUOTE"><begin quote>Originally posted by: HondaMechanic




Did you clean the air cutoff valve I believe that is what you mean by " the vaccum valve on the side of the carb" make sure it is clean and the hose is in good shape..

</end quote></div>


HondaMechanic, I know you know your stuff, as ive read a few of your replies, and your answers as always good. But i was unaware of any air cut off valve on the foreman 450es. I know the 450r and my 400ex have them, but i didnt know any utes had them. Could you post a pic or screen shot of where it is?
Im just interested in more info.
Keep up the good work.

 

 

Thanks, I learned something today.[img]i/expressions/face-icon-small-happy.gif[/img]