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06 ktm 400exc jetting

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I have purchased a neww 400 EXC . It seems to run Lean, I have to run for quite some time before I can kick the choke off. Also in tight situation, a quick throttle opening, the engine will cough and stumble some. Can anyone tell me how or what jetts to run for Indiana climate?

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Best advice is to go to the TT jetting forum and look at the jetting database sticky and see what others are running.

Also, if the bike is new write down the size installed in the manual or if used get a look at what's in now.

Also, look at this for a great explanation of what each jet does. Its from a reference to the FCR on a Yamaha but the carb is the same. The 1st graph is a great indicator of which jet to go after once you determine where the trouble spot is.

http://www.thumperfaq.com/jetting.htm

Personally, I prefer a smaller leak jet and very little play in the AP linkage and a larger than normal pilot.

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Here's what I tried for my 2005 KTM400exc. The results are awesome.

Here's the "majic" configuration that finally worked for me:

Stock KTM float Bowl

Honda diaphragm

KTM SX needle #4

185 main

FS 1.25 turn out

42 pilot

O-Ring on acc. pump

Timing screw on carb (right side): adjusted out until there is only 1.5 thread showing (this is the key) (that means the gap is closer than .10).

Adjusting the timing screw this way results in a very short but strong squirt. This was the final step that made a huge difference in how the bike ran.

- Bike pulls cleanly and hard all the way through the power range. No BOGS or stumbles.

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Agreed !!

Mods to the AP linkage can make a huge difference in the off idle snap.

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I mistakenly gave info on reducing teh leak jet size for the EXC. After tearing dropping the bowl on my 05 450 exc I was supprised to see that there is no leak jet. It looks like the passage is there but no changeable jet like the one on my o6 Yamaha Kiehn. I thought they were the same.

Does anyone know if the leak jet passage is functional or blocked?

Thanks

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My 400 is my first 4 stroke. I was very unhappy with the dealer supplied jetting. It's been a struggle to get a good running bike but this is where I'm at now.

170 main

JD red @ #6

42 pilot

fuel screw around 1.75

JD float bowl w/ leak jet

stock diaphram w/ stock cover

medium o-ring

stock pump screw setting

Bike runs great! Front wheel lifts well, good fuel economy, and doesn't overheat at all. Throttle response is great throughout.

I may try some other setups, but I don't know why.

Altitude for me is between 3000 and 4000 feet. Temps have been in the 90's.

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Honda p/n 16021-MEB-771

From previous "I mistakenly gave info on reducing teh leak jet size for the EXC. After tearing dropping the bowl on my 05 450 exc I was surprised to see that there is no leak jet. It looks like the passage is there but no changeable jet like the one on my o6 Yamaha Kiehn. I thought they were the same."

I read that some KTM's made after 05 do have leak jets in the bowl. Can someone confirm?

This must be the reason for the Honda diaphragm swap. On my 06 WR Kiehn the Leak jet is the way to control AP squirt volume. AP squirt is thru both the AP nozzle into the engine and the leak jet circuit. Increase the LJ size and the AP volume is reduced.

Confirmation anyone ??

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I noticed a 250SX-F with the leak jet float bowl, but it also had a brass plug in place of the jet.

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We called that a zero leak jet. I have a few that I've soldiered closed to reduce the leak to nothing in very cold weather.

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I have heard that the 250SXF comes with a float bowl with a leak jet, some models with it blocked, some with a leak jet installed. The 400, as far as I know has never had a stock leak jet.

There is a reason for the Honda Diaphragm; the longer post in the middle yields a shorter squirt. A dual sport might be an application where a longer squirt is wanted, though. With lots of traction (pavement) the motor won't spin up as fast and might use a longer squirt. 3 seconds (roughly the stock EXC diaphragm) is a bit long for dirt applications though, so most find the shorter squirt from the "Honda" diaphragm better. With the leak jet equipped Hondas, ironically, many are going to a longer squirt.

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I have purchased a neww 400 EXC . It seems to run Lean, I have to run for quite some time before I can kick the choke off. Also in tight situation, a quick throttle opening, the engine will cough and stumble some. Can anyone tell me how or what jetts to run for Indiana climate?

Stock jetting is way too lean. One of the 06 400's in my garage runs an EKR needle clip 2, honda diaphram, 45 pilot and 168 main. used on 4000 to 10,000 ft elevation.

The other 06 400 runs ELM needle 2nd clip, honda diaphram, 45 pilot, 168 main and a #35 leak jet. Yes I fitted a honda carb bowl to get the leak jet. I probably wouldnt do it again for the $50 it cost.

At sea level you can probably run the ELM needle without the leak jet and have a good running bike. Both the ELM and EKR needles are yamaha parts, EKR is for a 00 YZ 426, ELM is for a 03 YZ 450. Both needles offer better throttle response from 1/4 open and up. The EKR is pretty much same small openings as stock, but much richer 1/4 on up.

The best setting with stock needle was 45 pilot and clip 3, 178 main. Clip 4 was too rich at 7000 feet at small throttle openings.

John

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My 06 450 EXC was lean and I was never able to get it operating with the existing needle, etc. so I went with the JD kit and that corrected the issue with minimal tuning.

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