400ex jetting issue or something else?


Recently acquired 2008 400ex, 100% stock except street legal kit and handle bar  bike has never been apart very low hours still has nubs on tires previous owner says never had a problem on ridden maybe 30 times did see some sand..  had been sitting so I assumed the bogging was bad gas/dirty carb.  I cleaned and oiled air filter drained tank cleaned filter, pulled jets cleaned with carb cleaner, replaced pilot with 42.  resembled put fresh gas starts almost instantly will idle for ever, 1/4 throttle seems fine will even pull the front tires off the ground. at about 1/2 to 3/4 starts to bog stutter shutter what ever word you use for it.  wot throttle will cause bike to stutter even more if held at 3/4 in neutral it will start to sputter continuously some white smoke then dies hit the button and it starts back up.  Pump shoots a good stream gas checked ground on battery plug comes out black (obviously rich white smoke black plug)  cant figure out why stock main is 148 elevation is 4500' needle is not adjustable.  Any help would be greatly appreciated the weekend is coming.

Hard to say, but since you only replaced the pilot jet, I would go back and replace the main also.  Almost sounds like the main jet could be loose or maybe even fallen out into the float bowl.   I'm no expert, but rule out an air leak also by checking all the connections to the carb. It does sound like a carb issue to me.

Well some resolution, I checked everything swapped cdi, coil &  wire, and rectifier one at a time  from a running bike problem still there.  Swapped carb off running bike problem gone, running bikes carb had a 142 main, so swapped that into the other carb problem is back.  replaced float needle and problem is barley noticeable.  Is it possible that the factory jetting is just that bad I ordered a new float, it will be here in a couple days, I didnt try air box lid off I am kind of sick of looking at it. I can run through all the gears as long as I dont hold it wide open for any length it runs great.  I am getting a slight bit out the overflow after wot.  

My guess is you still have some gunk in the main.  Did you blow all the chambers out with compressed air?

He just said he swapped the main ?^ and also I'm having the same exact problems with my raptor so if any one can help it would be awesome

allways start out replacing ALL jets off the bat and clean the carb, every orface, as best as possible.  its better to knock out the problem the first time then have to go back and revisit it. 

allways start out replacing ALL jets off the bat and clean the carb, every orface, as best as possible. its better to knock out the problem the first time then have to go back and revisit it.

i just replaced all my jets and it's still giving me problems I've tried adjusting the air fuel screws every different position and all the pilot jets and other jets underneath the fuel bowl all stay tight right????

Well float came in, pulled apart again, installed partial reasemble test ride problem still there, I think it may be a worn needle, and or needle jet, ordered full rebuild kit and will replace I am going to swap the needle and needle jet from the working carb while I wait to see if I can pin point that as the problem before reubilding the whole carb, I have seen this problem posted on every forum out there and most of the threads end in no resolution, I will not leave the readers hanging on this one.   

Jake did you replace the needle jet and needle?

Well I have dual carburetors and I replaced both fuel air both main and both pilots

Let me know how it works out please

Okay so here is the update, after a great conversation with a local bike mechanic and one more trip into the carb.  I swapped the needle and needle jet (for those that dont know the jet that is visible from the inside when the butterfly is open that the needle slides through) problem is still there.  the needle out of the old carb (99-2005 had adjustable needles 05 to current do not), so I leaned it out 1 clip up stock is 3rd from top so I raised the clip to the 2nd notch, bike runs better not great, decided to try and lean it out a different way and installed k&n with outerwears and a whites e series I had in the garage, Bike rips like its supposed too.  The mechanic I talked to seems t think that even at our elevation (4500ft.) stock jetting (148 main) was just too rich, the local honda shop says they have not had any problems running stock jetting...Hmm For comparison I am running 170 main in my outlaw 525 (big three)  190 in a 450r (big three) both of those bikes run like beasts..Seems the whole problem was jetting too rich, I still plan to completely rebuild carb when kit comes in all new jets gaskets etc.  but for know it runs and on to modding the 700xx.....

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