boggin 400ex

[brianp25]

my 400ex will run good for a whille then all the sudden when u give it gas it bogs the motor out, but it idles fine, just when u give it gas. any ideas? its an 03 2nd owner no engine mods that i know of, does have exhaust and k&n w/o lid. the previous owner said he had the carb rejetted for the mods.....

[400exrider26400]

maybe your carb is clugged up
clean it

[<DRS>GPF]

does it help to choke it a bit? if not, then try running it without an airbox lid to see if it gets better.

[bigd's ex]

If you have an aftermarket pipe & open air box you need to rejet your carb. It's running lean & needs to be bumped up a couple sizes on the main & while your at it bump up the pilot jet to a 40 or 42. My sugestion is to read the stickies at the top of the page on jetting to get yourself familiar with it. Every bike is different, so there is no exact starting point when jetting your carb. But your problem imo is the jetting. Hope this helps. Here's a little something to read that may also help.

http://www.duncanracing.com/TechCenter/Keihincarbjett2004.pdf

[Snipe]

Could be airflow as well. My bike was running pretty well stock white bros full exhaust and UNI airfilter my stock air box was so constrictive it wouldnt run worth a crap, I lost all my throttle response boggin out. Took the lid off and it ran fine.

As for bikes being diffferent, I had to rejet to a 178 with a stock carb to get this stuff to put a brown on the plug and run perfect.

[brianp25]

it ran great when i bought it, and it had all the mods already on it,
i went throught the carb today and didnt find anything, started up ran fine for about 10 mins and back to the same thing, did notice that it sounded like it was backfiring through the intake? leaky valve maybe?

[honda400ex2003]

headgasket maybe or an exhaust leak? steve

[Snipe]

Back firing in the carb could also be it isnt on right and is drawing raw air into the carb that will usually do it as well.

[DuwBra]

i have a similiar problem, my 400 has always ran perfect, its been rejetted and everything, then yesterday i got it out to ride and it would bog really bad and backfire if i got on it, but ran ok at idle and really slow speeds. Any ideas? Its never done this before, it just all of a sudden started doing it.

[bigbad400]

both of you deep clean your air filters or buy a new one, anytime mine bogs like that i need to clean my filter. or the outerwears could be plugging up if you have one, they dont last long but they do help alot. try cleaning but you will prolly just have to throw away an outerwears sleave if that's the culprit, good luck.

[aDviSol2y]

Originally posted by bigbad400
both of you deep clean your air filters or buy a new one, anytime mine bogs like that i need to clean my filter. or the outerwears could be plugging up if you have one, they dont last long but they do help alot. try cleaning but you will prolly just have to throw away an outerwears sleave if that's the culprit, good luck.


You have it right on! To bad it took me 2 weeks to figure this out.......... I felt like an idiot when I took my outerwears off and my bike ran great. You must keep you filter clean and replace your outerwears often!

[bigbad400]

air is a BIG part of making a motor run no air no go. the manual says to clean your filter after every ride!!!! i dont... but i do clean it like every other ride or every 3 rides or so, sometimes more often in dusty conditions, gatta have that air flow!!!! good luck you guys.

[DuwBra]

i just cleaned everything and it did this, we even took the outerwear off and it ran worse.

[416exman21]

mine did the same thing the other day--i took my filter out of my gas tank and cleaned it-clean and retuned my carb - and i also put a inline fuel filter after between the gas tank and carb that way you can see the dirt and stuff... good luck

[DuwBra]

where is the filter, in the gas tank?

[416exman21]

ok to make it simple(where your gas on/ off knob is ----follow it to the bottom of your gas tank ---there is (2) bolts holding it in the bottom off the gas tank ---remove those 2 bolts - pull it out and you will see the filter ---clean it really good or get a new one---------------i cleaned mine with gas and some carb cleaner and put it back in--i also have a inline filter between the carb and the gas tank---that way it is easier to check and to get a extra filter for the gas to go through so it's a clean as it can get---try that and let me know what happens------and mine also would idle perfert but when you got on it it would backfire and die---i had to push it down the road to my house and it sucked

[dankbud42o]

Originally posted by bigd's ex
http://www.duncanracing.com/TechCenter/Keihincarbjett2004.pdf [/B]

this should be posted in one of the stickies. thanks for the link.

[MtnEX]

Originally posted by brianp25
my 400ex will run good for a whille then all the sudden when u give it gas it bogs the motor out, but it idles fine, just when u give it gas. any ideas? its an 03 2nd owner no engine mods that i know of, does have exhaust and k&n w/o lid. the previous owner said he had the carb rejetted for the mods.....

Mine was doing dead exactly the same thing all of the sudden...

Turns out it was alcohol content in the pump gas.

It had eat up my fuel line and I had a pinhole that was letting air in... didn't realize it until I started messing with everything and it started flowing the other way.... leaking gas...

I put on a clear fuel line, fired it back up and saw water passing.... so I drained the tank and found I had a nice cocktail of water and alcohol settle at the bottom of my tank, with the gas floating on top.