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backfire and popping
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Posted by: hemi400ex

2007 400ex just installed a hmf slip on, k@n air filter, lid on, and rejetted to 42, and 155, bought the adjustable needle and put it on the third slot. from idle to 3/4 throttle is great but at WOT the bike pops and cracks and some time backfires in all gears when i run them out, will a 158 or 160 help or is it because i don't have the quitecore in my muffler so its stright through now

Posted by: hornetgod13

Pull the air box lid off for trouble shooting purposes. Ride it with the lid off, if the condition gets better than you need to lower your main jet. If the condition gets worse than raise you jet size.

Posted by: hondaman954

Hi I just installed the same setup on my 400 ex and it is awesome but: leave air box lid off (ok as long as your not mud swamping) 42 kein pilot, 170 dynojet main-w/adapter in jet kit. 3.5 turns out on fuel screw, Third clip on dynojet neddle. Runs awesome. I am also at sea level. Try that and see how you make out. You sound like like you r way too lean on wide open throttle.

Posted by: hemi400ex

quote:
Originally posted by hornetgod13
Pull the air box lid off for trouble shooting purposes. Ride it with the lid off, if the condition gets better than you need to lower your main jet. If the condition gets worse than raise you jet size.

lower would be 152 and higher would be 158 right so sence its only doing it at WOT only the main has to be fixed right? the pilot, needle, and fuel screw r all ok right ?

Posted by: hornetgod13

Based on how you described the issue, it sounds like it's only the main jet. 152K would be down and 158K would be up.
The adjustable needle is on the 3rd slot down from the top right?

Posted by: 400exrapes

check your plug. then i would say go down to a 152 because i was too rich with a 152 and 42 on my quad. I talked to a carbuerator mechanic yesterday and backfires out of the exhaust means too rich and if toolean the backfire will be in the carbuerator

Posted by: hemi400ex

well i ran it today i removed the air box lid what an importment the only backfireing now is when i go from WOT to no gas at all slowing down for turns then it screams back to life intill i let out again so i'm going to drop down to a 152 and see how that works