Popping noise

[nj87ttype]

I have a full White Brother's exhaust for my 300. When decelerating it makes a popping sound. It does it more if I'm in a higher gear like 4th or 5th & let off the gas. Is this a normal thing for W/B exhaust, or does something need to be adjusted?

[04'400ex'er]

J E T T I N G.

[Florida400EX]

You're running too lean, and it's causing your motor to backfire. You will need to rejet, and theres many guys on here that will help you get it spot on. Until you jet, don't ride it too hard.

[cals400ex]

on the bottom of the carb there should be a bronze colored screw that you adjust with a flatblade screwdriver. turn it counterclockwise 1/2 a turn or so.

[nj87ttype]

I dont know why I would have to re-jet. My carb is already re-jetted with the correct jets. I'll try to adjust the fuel mixture screw. Thanks for the replies.

[cals400ex]

how do you know it is jetted right??? jetting changes at the temp, humidity, and elevation changes.

[nj87ttype]

I know its jetted correctly because the carb came off of my friend's 03' 300 EX. (Same year as mine). He had the same exact mods as I do now when he had the carb on his quad. I found out though that it was running too lean. After a little bit of testing & tuning I was able to get it to stop making the noise, & its running like a champ now. :cool: Thanks for your info everyone.