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View Full Version : think my 400ex is running lean but don't know best route to go


biker2551
09-02-2010, 02:39 PM
just got it in trade it's a 2001 400ex was told it has a cam and has been jetted however that's all i got for details. i know the cam is there cause i can feel the power difference, just i don't know what stage or brand. it has a dg slip on muffler w/o spark arrestor. the exhaust just seems a bit hotter than it should so i think it's running lean. it also backfire when let off on the gas. rather not blown the motor so was wondering what the best route i should go to fix the backfire issue withou any positive confirmation on anything.....yet
biker2551
09-02-2010, 02:45 PM
it has a stage 2 hot cam and the guy isn;t sure what size jet done. but after reading the posts here i know how to check that out. but is the backfire normal? and the possible overheating. the muffler has been changed but it still has stock headers.
honda400ex2003
09-02-2010, 03:27 PM
possibly a f/a screw adjustment for the popping on decel turning it out will help most likely. If you are at 3.5 turns out and it is still doing it, then it is time to up the pilot. I would suspect that around a 152 is in there. Either find out or take it apart and find out. check both the pilot and the main while in there. as for the heat, it may be possible that it has a higher compression piston in it. that will cause more heat. a bit of popping is alright also but not accessive to where it is getting quite loud and very noticable. steve
biker2551
09-02-2010, 04:02 PM
checked the plug looks good, a LITTLE dry carbon but not to where it worries me. when i have a bit more time....hopefully this weekend....i'll take the carb off and take a look at the goods. the exhaust itself is LOUD...sounds like a harley doing 60!! but i feel better after checking the plug that it's not going to blow up on me......unintentionally that it. thanks for the advice and will update when i get it done? what does the price for jets go? last time i knew it has around $22 for a pack of 5 mains.
honda400ex2003
09-02-2010, 04:05 PM
you can get them seperate for around 4-5 bucks. at least that is what i pay for mine. if you need to order jets go to jets r us .com. they have a great kit and also all the individual ones you could need. it sounds like it is alright though. maybe go out a 1/2 turn on the f/a screw and that would be about it. steve