Fix Keihin Carburetor on KTM / Husky 300

The 3 modifications you need to fix the Keihin Carburetor on a KTM 300 so it will run at altitude without loading up and or having a mid stumble. Including Jetting, Needle, and Slide modifications to fix power at the mid to top transition and the idle to mid transition. There is also a jetting chart at the end for use after modifications.

[@RichPlakas]

Great informative video. Starting using a NEDH needle on our KTM 205 XC but haven't messed with the Pilot or Slide...yet!

[@brainstain22]

Great info regardless what bike you have. Thanks for sharing.

[@barswapmedia]

I’m glad it was helpful. I was so frustrated with the low end at altitude. I just hope this saves someone the years of experimentation it took me to make my KTM 300 run the way my YZ 250s ran all the time.

[@enduro-parts-aus]

Interesting 👍

[@taylorbohach5386]

Per the jetting chart at 7:23, the NECJ needle position should be leaner at 2000' (2ED) vs. 4000' (3ED). I would expect the opposite. Also, the AS setting is the furthest in (1.5) at 10,000'. I would think the trend would be to back the AS out further at higher elevation to help lean out the mixture (opposite of what the chart suggests).

[@barswapmedia]

If you look at a jetting chart of the interaction between your pilot jet, the air screw and the needle, they all interact with one another as you transition from your bottom to your mid. Because of this, when you lean out the carburetor by installing smaller pilot jets at altitude, you cannot assume that the air screw position would need to be more open. Your changing the entire balance of the carburetor every time you change the pilot jet, main jet and the needle position. I’ve raced these carburetor settings on a KTM 300 from 2000 feet to 13,000 feet for the last five years depending on temperature and humidity, I occasionally have to make adjustments to my air screw position but it’s normally only a half turn or so. I’m not sure if it says so in the video but those jetting numbers are for a 38 mm carburetor. If you have a 36 it will be slightly different.

[@barswapmedia]

If you want down and dirty testing, I would put the needle in the third position and leave it there with the air screw two turns out. Start with 2000-168/38 4000-165/35 6000-160/32 8000-158/31 10,000-155/30

[@taylorbohach5386]

@@barswapmedia Thanks for the notes. I'm interested in trying this jetting on a 2003 300 EXC w/38mm Keihin. It looks like my OEM slide is a #6.5 so maybe I should start without grinding my slide. I see your comments below stating you did this on a 2013 300. From the owner's manual, doesn't that bike come factory w/ a 36mm carb and #7 slide?

[@barswapmedia]

@@taylorbohach5386 I’m not sure what the OE carb is but I believe you are correct that it’s a 36, I had purchased the bike used from somebody and it came with a 38 mm on it. The cut in the slide I made was a number 7 slide

[@jeremyfisher1570]

Great video, do you think that Necj needle would work at say 500' elevation? Thanks

[@barswapmedia]

I think the lowest elevation I've had my bike at is about a thousand feet and it ran great so I would imagine it works all the way to sea level. That needle was the OEM needle for Suzuki 2 strokes with the 36mm Keihin

[@jasonstevens4192]

Nice info! Is there a #7 slide if one doesn’t want to modify? Also, what mods to your 300? I have a 19’ 300xc, RK Tek head, SX ignition. Currently testing with a 36mm pwk, it has the N8RH needle#3, 168m, 38p. Riding Penrose thru winter but will be high country machine for sure!

[@barswapmedia]

I have done this on a 13 and 14 300, One has a S3 head the other has .003" deck mill on the OE head. Both have V forces Reed and SX CDI. You definitely can purchase a different slide and achieve the same result, it is really easy to modify the OE slide though.

[@jasonstevens4192]

@@barswapmedia appreciate the feedback and all of the testing you have done to nail down these numbers(jetting).

[@barswapmedia]

Yes, you can purchase a #7 slide with the same change made to it for around $150, the 300 comes with a #9

[@jasonstevens4192]

@@barswapmedia just found slides on Motorsport for 69$!

[@barswapmedia]

@@jasonstevens4192 That's not a bad price. The OE slide is $195.00 on there right now.

[@2WheelDerness]

the chart in the end is for PWK 38 or 36mm? I have a older GasGas ec300 with full body PWK36 and runs fine but cant adjust the idle... the air screw is not making any difference, tried with 40p, 45p, 48p, P. think I have N1EC (or N1ED) on 3rd position and main is 175. runs ok just wont idle perfect... after a while will die or stay to high. Changed all sealings inside, new top and bottom end, reed valve ok, no air leak... dont know what to follow next.

[@barswapmedia]

I have a 38 mm on mine, I have a buddy with a 36 mm on his 300 with the same slide cut. It seems to benefit the bike, regardless of which size carburetor is on it. Those seem like really big pilot sizes for 300. I feel like those pilot sizes would be more conducive to a 250. The increased vacuum from the cylinder of a 300 requires slightly smaller Jets. The largest pilot jet I’ve ever put in my 300 is a 38

[@2WheelDerness]

@@barswapmedia thanks a lot, I will order some smaller pilot jets, I think is default slideer 7 on mine, need to check.

[@xtremeairvents]

I live at 7000 feet. My ‘13 300 definitely feels rich on the pilot. Do you have any more details on which pilot you ran at which altitude?

[@barswapmedia]

At 7k a 158, 32, NECJ needle in 3ed, AS 2 out, that jetting should be good from about 6,000 to 8,000 and would run pretty well up to 9,000. It's what I run at almost all the Enduros in Colorado. Below 6,000 I switch to, MJ 160, PJ 32, NECJ needle in 2nd. This is my Colorado front range setup for Hare Scrambles and it runs fantastic from 5,000 to 7,000. If you have not cut your slide (or purchased a #7 slide) this jetting will probably not be correct. Without the slide modification I could never get my 300 to run properly above 5,000 ft no matter what jet combination I tried.

[@xtremeairvents]

Thank you! Last question, what size is the sanding disk?

[@barswapmedia]

@@xtremeairvents 1.5" and I used the 120 grit. It's just one of those inexpensive little drum sanding wheels that you can put in a drill they should sell them at pretty much any hardware store. It will probably come in a kit with the little rubber sanding drum and then three or four different grit drums to go on it. After I did the sanding I used a Scotch-Brite wheel on a Dremel tool to just clean up the scratches from the sandpaper.

[@xtremeairvents]

@@barswapmedia awesome thanks for the info and video. I’ll be doing this immediately. Just ordered the needle from Motosport.

[@amigosdostrilhosteam3950]

Hello, i am Rogério, setting keihin 36 mm, ktm exc 250 2017, Portugal - Porto

[@donfunke625]

So with all those jets, how often do you change them? Obviously not during a race. Do you change them based on temperature? Do you use different ones for all the different elevations? What about a race that starts low and goes to high altitude.

[@barswapmedia]

If you want your bike to run properly you need to jet about every 2,000' in Elevation. For temp on the 300 the air screw can make enough change. When racing I always jet for the average raceable altitude, it might not be perfect if there is drastic change like Shady Burro where we go from 8,500 up to 13,000 but in that case everyone has that problem that's not on TPI.

[@tomreese3626]

My 2014 TE300 OEM slide is a #7. (The #7 slide is available at JD Jetting) Cannot seem to find pilot jets smaller than 35. Any idea where to find 30 and 32 pilot jets? Thanks for the great info in your video. Going to try that NECJ needle.

[@barswapmedia]

I purchased them at Performance Cycles of Colorado. I believe Slavens racing has them as well. Another option, you can find them on both Amazon and eBay.

[@RB25GU]

Would that be the same as installing a number 8 slide?

[@barswapmedia]

It is similar, I have never put a set of calipers on a #8 slide so I don’t know exactly how big it is, but the slide cut I made is very similar. I think my current slide it’s actually between 8 and 7 and it runs amazing all the way up to 13,000’ (with jetting changes)