backfire!! help

[astro360]

I was wondering what would cause a backfire and my header pipes to glow red hot? I live about 1000ft above the sea, temp at about 35-45 degrees. my bike is a 03 400ex it is all stock with 40 primary jet and 148 main with my needle on the 4th clip and my fuel screw at 1.5 turns out. I talk to my dealer and they said to put it on the 4th clip and that would help but it didn't. can u help?

[2004TRX450R]

Just out of curiosity what dealer did you talk to? The reason it didn't help was because that isn't the portion of the carb that is effecting the backfire. I'm assumeing it backfires on decel as that is the most common case. Try turning the fuel screw out to 2 or 2.5 turns. The reason it backfires is because it is lean. With the colder weather we have been haveing it makes it run a bit leaner. It may or may not help with the header glowing as that is kinda normal when it is just sitting there idleing or when going really slow because there is no air moveing across the pipe to help cool it.

[astro360]

the dealer said it would help with the pipe glowing red, I didn't say anything about the backfire because it happen after i put it on the 4th clip, the dealer was lynnwood cycle barn. also my pipe was glowing at wot in 3rd and 4th gear!!

[hondarider2006]

Turn your mixture screw out to 2 1/2 turns, and put a 150mj in and see what happens:)

[2004TRX450R]

I'd put the needle back where it was if that is what started causing your backfire problems. If it is glowing at WOT then that is another thing. First off where are you rideing it? Is it in the snow? When riding in the snow the engine and exhaust will get very hot because it is revving up a lot but you aren't moveing a lot. If it is glowing when you are moveing fairly fast then that may be another thing. As stated try going up a size on the main and see what it does. With the temps getting colder out it will run leaner wich could cause that. Also next time deal with I-90. That is where I work and we'll get you set straight.:D

[cals400ex]

Originally posted by astro360
the dealer said it would help with the pipe glowing red, I didn't say anything about the backfire because it happen after i put it on the 4th clip, the dealer was lynnwood cycle barn. also my pipe was glowing at wot in 3rd and 4th gear!!


if it is glowing at idle, increase your pilot jet size and/or turn the fuel skrew out some
if it is glowing at 1/8 to 3/4 throttle, raise your needle by moving the clip DOWN one position on your needle
if it is glowing at full throttle, go bigger on the mainjet