KTM 300 XC-W jetting woes

I can't seem to find the happy point on my jetting. It's either too lean or too rich.

 

The factory recommend settings are too rich and cause me to foul plugs regularly. I've tried going up a notch on the needle. Plug looked very nice but started hearing a little bit of detonation. It's like I need a notch in between the 3rd and 4th setting.

 

Current setting which is too rich but, what is factory recommended:

 

165 main

35 pilot

N2ZK needle on 4th position

 

gas mix is 60:1 - 93 oct. with motrex

 

Any suggestions?

I saw you posted something similar in another thread - this is a 2011 300XCW correct? Houston TX is about 70* temp, 60-70% humidity and about sea level.

 

If the motor is stock it will have a tough time with the needle in the #4 clip position - too rich. You stated that you are a beginner at jetting so to be sure this is with the needle clip in the 4th position from the top. If the sound that you heard in #3 position was more prevalent under deceleration or you had a little bit of a fast hanging idle when coming to a stop after a hard run, it is because the 35 pilot is a bit lean from the factory. I have had better luck with a 38 pilot when I was using KTM needles. The 165 is close but will depend more on your riding conditions. You can try richening the airscrew (brass screw on the petcock side of the carburetor) , by turning it clockwise - but I think you will need a 38 regardless. You can get a pilot or main jet at any bike shop or japanese dealer parts dept. Tell them it is for a kehin pwk from a CR/YZ/KX/RM 250 2 stroke - it is usually cheaper than the KTM dealer.    

 

I was disappointed in my 300s power when I bought it new.  My 250 had more punch and was easier to ride as well. After a few weeks of tweaking the jetting, it became a pleasure to ride with a better range of power and zero spooge from the silencer. I have run most KTM needles, honda needles and JD jetting needles and had the best results with suzuki needles. If you are willing to take an $11 gamble on the advice from an anonymous internet poster, order a NEDJ suzuki needle part number 13383-37FM0 . The original application is for a 2008 RM250. You can get them from any suzuki dealer or Motosport.com now has them back in stock. Install it in clip position #3 (middle) with a 38 pilot a 165 main and begin with the airscrew 1.5 turns out.

 

This will run cleaner than any KTM stock needle for a fraction of the cost of a JD jetting setup. If you test with it and like it and want to do more fine tuning I can forward a full jetting tutorial that will decipher the suzuki needle codes and the effects of eac carb circuit. If the motor is in good working condition I have a feeling that the baseline tuneup will be 95% there and will be more dependent on how angry you want the bike to run at wide open throttlde

Yes its a 2011 KTM 300XC-w all stock, 4th position from the top of the needle, Houston Texas.

 

You are right that I heard the detonation on deceleration.

 

Would a BR6ES plug and/or 104 octane gas help with the fouling with the needle in position 4? 

 

I'll give the needle and jet you stated a try.

 

What was the difference in performance with the setting you recommend vs a JD jet kit?

You have several issues working against you. The 35 pilot jet is too lean and will not supply enough fuel on deceleration when you close the throttle. The needle is too rich so it will be lazy and probably leave unburned fuel in the motor and exhaust, darkening the plug and oiling the silencer. Your main jet is close and will alternate between a 162 and 165 depending on your specific needs.  

 

Spark plug heat range and race fuel will not cure jetting issues. I run 94 pump gas with ethanol  :(   in a modified race motor and only have minor detonation issues when it starts to run really hot - like slow rocky hillclimbs in mud when it is over 90*. If you race 20-30 enduros and hare scrambles a year race gas gets expensive and not always easy to find your specific blend when you travel.

 

There are 3 primary tuning circuits on a PWK:  pilot jet / airscrew (0-1/4 throttle) Needle/clip position (1/8-3/4 throttle) and main jet (3/4+). There is some overlap but this is where they are most prevalent.

 

Oily silencers usually come from needle issues, fouled plugs are generally needle or main jets.  

 

Besides the pilot jet, you can fine tune the idle mixture  with the brass airscrew located on the side of the carb on the petcock side closer to the rear of the carb. Clockwise richens the mix, CCW leans it. The usable range is 1 turn out from lightly seated to 2.5 turns out with 1.5 turns out as a baseline for any new set up.  If the bike continues to run better as you keep going in either direction and you reach the end of the range it is time to change the pilot jet. 35 is the leanest pilot jet made, with 38s and 40s being the most popular choices for 250s and 300s.

 

Changing jets: since you have already changed the needle you know the basics - loosen the carb clamps at either end of the carb, turn it slightly to gain straight access to the 3mm allen head screws on top to remove them, carefully pull the slide out of the carb exposing the slide while it is still attached to the throttle cable. I carefully hang the slide by the cable on the exhaust pipe to keep it out of the way. Now rotate the carb so that the carb top is pointing toward the exhaust pipe exposing the float bowl access plug. The carb top may contact the pipe as you turn it so do it gently but forcefully. You want to turn it just far enough to get a wrench or socket on the bottom drain plug (14 or 17mm depending on year). Loosen it and put a small rag underneath to  trap the fuel. If I know I am doing a jet change I will run the bike with the fuel off to help drain the bowl before I take it apart. With the plug out you will see a 6mm brass hex jet and a small slotted head brass jet next to it  but much deeper in the carb. I will lay on the ground to see it if I cannot feel it with a small screwdriver. Unscrew the pilot jet, screw in the new pilot gently seating it in the carb and start putting it back together.

  

JD jetting kits are a great option for beginners that want to set it and forget it. It is $80 and includes 2 needles and jets. I still have mine but only could use the blue needle and the jets were too rich on the pilot and too lean on the main when I followed the supplied tune up. It is a good kit, but not something that worked well for my 250 or 300. Weather conditions vary widely across the country so that is why new bikes are never perfect - they need to be dialed in for weather, elevation, terrain and rider preference.

WOW...I just purchased a 2012 300 XC-W.......this is some awesome information :thumbsup:

@ Motorhead 1812

 

The Suzuki needle and 38 pilot jet are on back order but, I did get the JD jet kit in. I was hoping to go with the Suzuki needle first but, I'm going to have to wait I guess.

 

The JD jet kit comes with 38 PJ, red needle, blue needle, 152, 158, 162, 165 MJ. For a starting point it's recommending 38 PJ (same as you), Red needle on 4 position from top, 162 MJ and AS at 1 1/4 turns out.

 

How close will the JD kit get me to the Suzuki needle?

The Suzuki needles may be discontinued but not yet showing it on the dealer ordering system. Motosport was one of the last vendors showing any of them in stock. The JD kit will get you very close after you have spent some time fine tuning for your tastes. JD's baseline will be a solid starting point for your weather conditions. 38/Red#4/162 will give a clean responsive curve that should be close for your needs. Try it first and make some mental notes about what you do or do not like and in what part of the throttle range - i.e. 1/4 throttle is clean, but @ 3/4 throttle it revs quickly but the torque falls flat. Set the PV back to the OEM spring (yellow) and preload setting (turned in so that 2 or 3 threads are visible) to eliminate any crazy settings the previous owner may have tried.

 

Try it out in your typical conditions and go from there. When I used JD needles I ran the 38/Blue#4/165.  The blue needles have a slightly richer diameter than the red with the same clip positioning. My local conditions allow for richer jetting (dense air quality, lower humidity and sandy terrain) so my notes can steer you in the general direction, but you will need to make it work for your needs. In a few weekends of testing you will have needle changes down to 5 minutes flat.   

You have several issues working against you. The 35 pilot jet is too lean and will not supply enough fuel on deceleration when you close the throttle. The needle is too rich so it will be lazy and probably leave unburned fuel in the motor and exhaust, darkening the plug and oiling the silencer. Your main jet is close and will alternate between a 162 and 165 depending on your specific needs . . . .

 

This was very well put. I learned quite a bit. 

The Suzuki needles may be discontinued but not yet showing it on the dealer ordering system. Motosport was one of the last vendors showing any of them in stock. The JD kit will get you very close after you have spent some time fine tuning for your tastes. JD's baseline will be a solid starting point for your weather conditions. 38/Red#4/162 will give a clean responsive curve that should be close for your needs. Try it first and make some mental notes about what you do or do not like and in what part of the throttle range - i.e. 1/4 throttle is clean, but @ 3/4 throttle it revs quickly but the torque falls flat. Set the PV back to the OEM spring (yellow) and preload setting (turned in so that 2 or 3 threads are visible) to eliminate any crazy settings the previous owner may have tried.

 

Try it out in your typical conditions and go from there. When I used JD needles I ran the 38/Blue#4/165.  The blue needles have a slightly richer diameter than the red with the same clip positioning. My local conditions allow for richer jetting (dense air quality, lower humidity and sandy terrain) so my notes can steer you in the general direction, but you will need to make it work for your needs. In a few weekends of testing you will have needle changes down to 5 minutes flat.   

I got lucky and now have the NEDJ needle on it's way. How will I know when I have my jetting dialed in? Can you post pic's of what you spark plug looks like after you dialed in your jetting?

Plug coloring is not as useful with todays pump fuels. You are looking for a color on the lower part of the plug's porcelain similar to a coffee medium. After that it comes down to personal preference. A late model 300 with very crisp jetting is difficult to manage in the woods. It is exciting to ride around sand pits and MX tracks, but it will tire out most riders during a 3 hour GNCC. Most racing 300s are jetted marginally rich; not boggy / drowning in fuel rich - just slightly fatter than peak dyno power. Start with the suggested jetting and see if you like it more or less than the JD needles.

UPDATE:

 

Had a chance to play with the jetting over the weekend.  Seems like my bike liked the JD blue needle in the 3rd position the best. I tried the 4th position but, I could feel the power starting to fall off.

 

Current jetting:

 

JD Blue needle with clip in 3rd position

38 PJ

162 MJ

1 1/2 turns on AS

 

I do get a single "ping" when I chop the throttle but, I contacted JD jetting and they said it could be carbon build up (very possible with how fat it's been and as slow of a rider as I have been). They said it's nothing to worry about and their bike does it too.

 

Think I'm going to change the the MJ to a 165 just to see if it's dialed in on the top end at WOT. The Suzuki NEDJ was a little lean for me. It might be a good needle when it cools down again.

 

Just for the fun of it I changed back to the factory KTM needle just too see how much of a difference I had made. Man it was a night and day difference. It was way easier to stay on the pipe in the trails and in the long open areas, it just rips now.

 

Thanks motorhead 1812 for the replies.

Wow!!! This is a great thread. I have been pulling my hair out trying to jet this 300. I get that lean break-up happening around 1/8 to 1/4 throttle. The just off idle range is SO crucial to me because for my riding it's right where the bike wants to be to cruise. I can lug it a gear high and open the throttle just past that 1/8 position until it cleans up, but I inevitably accelerate and cannot hold a steady speed without letting off the throttle. Plus it seems when I'm doing more technical stuff it's usually right in the throttle range that I'll get that SO annoying lean miss...

I too get some popping and hanging idle during deceleration. With the AS any more than 1.5 turns out, if I wack the throttle wide open from idle with the engine in neutral I'll get that lean hesitation. Funny thing is every source seems to suggest setting the AS by adjusting it to where the idle rpm is the highest, then adjust from there to clean up the off idle transition. Well, if I do that the pilot circuit is WAY too lean. I have experimented with essentially every setting and currently I'm running 162 main (was running good with a 165 but since I so rarely run it on the main I switched to the 162 in anticipation of the warmer weather), stock needle in 3rd pos, 35 pilot, AS 1/3 out. Right now at 7*C (44*F), 650 meters (2130ft) above sea level, and RH of usually less than 20%....it's early in the season, but mid season temps usually average around 24*C (75*F) and easily get up to 35*C (95*F).

As I understand it the air screw loses it's effectiveness once it's turned in more than a turn from it's seat. The KTM jetting chart is misleading (to me) because it states AS setting of 1....leaving me to believe that's the starting point (center of it's range)......given that I am riding in about the coldest temps I will all season, it makes sense that the AS likes to be in more than the suggested 1 turn......but 1/3 out?!?!?!?? In my mind that's suggesting a richer pilot is in order. I'm really at my wit's end because I spend WAY more time these days fiddling around with the carb than I do riding......not only is it not fun for me, but also not fun for my riding partners (my two son's).....I really just want to set it and ride, and just make little seasonal adjustments during bigger swings in conditions... Am I being to fussy? Should I just open the throttle past the point where it breaks up and not worry about it? I just feel a great bike has even greater potential, and am determined to get it right...

I get VERY close to clean all the way through with this set-up and switching to a 38 pilot was going to be my next move.......then I come on here and learn that it's widely accepted that 300's prefer a richer pilot!!!! That is a perfect example of what makes this site SO awesome!!! The bike is awesome, but I know it could be SO much better with a cleaner off idle transition....

Had been considering JD, but this Suzuki needle has me intriqued...

Oh...the bike is a 2007 300xc-w bone stock...

Edited by Fattonz

Earlier 300s are more difficult to jet. Here is a fact to consider: the leanest pilot jet made for a keihin PWK is a #35. There is nothing leaner. What are the odds that a 250 or 300 KTM race bike would run optimally with the leanest jet made for a particular carb?

 

A 38 is an good start and will make the transistion from idle/pilot to the needle circuit smoother. It is $4 and relatively easy to change.

 

The idle speed method works for fuel adjustment screws on 4 strokes and automotive motors. I prefer a different 2 stroke AS method: if the motor is warmed up, pull in the clutch or put it in neutral - you should be able to crack the throttle and free rev it wil no bog or hesitation. When all of the circuits are set for clean running, 1/4 turn on the AS will make a real difference in how the bike reacts at lower rpms.

Just to follow up. It appears this is what works for me with current weather conditions:

 

38 PJ

JD blue needle on #3 position

165 MJ

2 turns on AS

 

For me the JD kit was worth it to try several "known" settings that have worked for others. It is a little pricy at $80 but, it got me in the ball park with all it's jets and needles and I just spent a day playing with the settings until I found the right set up for my conditions and my riding style. I've got to where I can change jets and needles pretty fast.

 

I also had hanging idle problem with the 35 PJ.

I have four 2T bikes in the garage, all with Keihin carbs....hence I tend to keep a lot of jets around. Would you guys believe a 38 pilot was the ONLY pilot I didn't have???

Anyway, a quick trip to the dealer and the 38 is installed. I'll report back the results...

Well, the boys talked me into a ride tonight. I was out for about an hour and the #38 pilot is a vast improvement over the #35. The transition from idle to the needle circuit is much cleaner.... With the 35 the sputter wouldn't clean up until nearly 1/4 throttle, whereas now it sputters a little off idle but cleans up @ about 1/8 throttle.

There is still some popping as it idles down and a bit of hanging idle. Just to reiterate, I am at 650 meters. The conditions today were 10 degrees Celsius with 33% humidity... I settled on an airscrew setting of 1.3 turns out. I can almost live with the bike the way it is right now, but think there's still potential to clean up that off idle sputter....

I'm tempted to try the #40...

You know what amazes me is that this bike has had the 35 pilot in it since it was new in 2007...how the heck could the guy have ridden like that? Apparently he rode it a lot above 2000 meters.... I suspect it would have been even worse at that elevation...lol.

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