2009 400 xc-w bogging problem.

I recently bought a new 2009 xc-w (a week ago). Installed the JD jet kit to exact spec and am still having a bogging problem off the bottom end. Does anyone have any ideas what this could be. If the bike sits new for two years, can the carb get dirty? I'm at the end of my abilities with this thing and it's starting to get very frustrating.

any help would be really appreciated.



I would say your pilot is clogged.I went up one size on the pilot than what the jd kit said.Did you put the oring on the ac pump?

no, I did not put the o-ring on the ac pump. would that make a difference?

put the small o-ring on. it doesn't seem to make a difference.

Clogged carb. Did you clean it at all before intalling the jet kit? Take the pilot jet out and fuel screw and blow the passage ways out with carb cleaner. And yes that o-ring makes a big difference with the bottom end bog. And take the screen off the end of the muffler as well its very restrictive.

Did you put the little spacer on the AC pump diaphram ? If you did and your bike has a leak jet (some 09 did, some didnt) it will bog badly. Chek to see if you have a leak jet if you do remove the litle spacer off the diaphram (bit tricky but you can do it) and you will be good to go. Use the big o-ring

Did you put the little spacer on the AC pump diaphram ? If you did and your bike has a leak jet (some 09 did, some didnt) it will bog badly. Chek to see if you have a leak jet if you do remove the litle spacer off the diaphram (bit tricky but you can do it) and you will be good to go. Use the big o-ring

Iam thinking (its been awhile) jd sends a longer spacer for the diaphram.You can do that or put a bigger leak jet in.

yes, the carb was totally cleaned and the jets were pulled out and cleaned as well. I did put the little spacer on the AC pump. the bike does have a leak jet so I might try to remove the spacer. it looks to be a bit difficult.

here's what James at JD said. Have yet to try it.

The thicker O-ring should be installed on the accelerator pump linkage for a faster response.

Make sure the fuel screw setting is set for a good idle mixture when the motor is fully hot as described below-

Setting the fuel screw mixture-

Try adjusting with the motor fully hot, and turning the fuel screw inwards until the idle slows or runs rough, then turn outwards 1 1/4 turns from this position. For example, if the idle slows or runs rough at 1/2 turn from closed, then set the fuel screw to 1 3/4 turns out (1/2 + 1 1/4 = 1 3/4).

See- http://www.pbase.com/jdjetting1/image/82894252 to understand how the fuel screw can affect the idle speed and air/fuel mixture at idle. The target range for the air/fuel mixture is near 12.5 to 13:1 at idle.

The spacer might need to be pulled off if there is any issue with the accelerator pump. In some cases the pump can have a slightly clogged passage or may not be squirting as much as other bikes. In this case the spacer will reduce the pump squirt too much. Remove the spacer by using vice-grip pliers to pinch the very end, and then pry the spacer off with a flat blade screw driver.

I would recommend using the Red marked needle set in the #5 from top clip position, and a #178 main jet, as an estimate for good response also. The Red marked needle is usually set in the range from #4 to #6 from top clip positions.



If you completely get rid of the bog on the bottom, please post up what you did. I've been fighting this for 2 years on my 09 400XCW. Most of the bog is gone, but from very low revs, if I snap the throttle with load the bike still falls flat on it's face.

Here a easy thing to check, simply remove the airfilter, use a flashlight to look in the boot at the nozzle and make sure you are getting a squirt when you twist the throttle. Might as well get a stopwatch and time your duration while your at it. I say this because my new 2010 XCW 530 SD came with a clogged A/C pump nozzle. I was very surprised. I had to pull the carb and use compressed air with a rubber 90 degree hose on the end to get it cleared. I never rode it before catching it (I was really just wanting to time the duration to see what the new leak jet was set at), but I'm sure it would have bogged badly.

put the large o-ring on and removed the spacer. huge step backward. It barely runs now. I'm starting to get very frustrated with this thing.

It makes me sad to see so much misinformation. Read this, ask me for guidance if you are confused. It is very important to follow the steps outlined in the thread EXACTLY. Once followed, you will not have a bog. Period.

How to eliminate the 'Bog'

I'll give it a try. Thank you.

What size piolit do you have?I went up one from what jd kit said.Also you need either the spacer on the diaphram or a bigger leak jetfor the fuel squirt.Double check to make sure the piolt jet isnt clogged up the passage is so small.Hold it up to the light and look through it to see if its clooged.

I have mine running (near) perfect at sea level in California SF bay area.. unless it's a dirty carb issue you will most likely cure it with the AC pump mod and timing screw.. I had to play around with mine a little to get it right..also..make sure you set the air/fuel screw as JD recommended.. and for this you have to have an aftermarket screw to be able to adjust on the fly..might be obvious but thought I would add that..

also.. I have talked to people who swear by this thing

I was planning on buying it but managed to get mine pretty close to perfect without.. but seems like a worthy investment.. dirtrider swears by them in their review of the 400xcw

One last thing.. make sure when you are testing you are riding the thing under load... if you are just wacking the throttle in your garage you won't get very far.... hang in there ..sweet bike once you get it dialed.. I had a frustrating few weeks as well but never think about it anymore.


this is what I've done so far. it's still running awful. Still HUGE bog off idle.

JD Jetting kit with his needle and stock needle, multiple positions

Thick/thin o-ring on the AP Linkage

Stock 42 pilot (everybody seems to like this best)

178 Main per JD

40, 50, and 70 leak jets

Tried with and without JD's little cap that goes on the AP diaphram

Made sure the AP stream went straight down the bore of the carb

Messed with the AP timing screw

Fuel screw adjustments with each try

Cleaned carb as best as I know how, sprayed out each port/jet

Did you remove the screen on the end of thr muffler? Big difference without it.

did you make sure that the oring and spring went on correctly when you installed the aftermarket fuel screw? I would take that out and make sure that it was assembled correctly.... make sure that the oring is present and sealing good.. that would make it run weird... something to check anyway.

yes, the screen was removed from the end of the muffler.

we also made sure that the fuel screw was assembled correctly.

thanks for the help.

not that this is a solution..but i would find a local shop/mechanic that knows ktms and let them fix it... super common with ktms and jetting being an issue... in other words throw the checkbook at it and get a second pair of eyes on it... then go ride it and be stoked..you will forget about the money you spent... its a sick bike when its running.. i know I almost lost the plot trying to fix my bog... somehow i did.. but that was the next step for me..

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