I thought I would post this to help any one struggling to getting the jetting right on there KTM I swapped out the original Mikuni out of frustration and went to a Keihin PWK 38 because I consider this carb better suited to the bike. I bought a JD jetting kitwhich in hindsight was probably caused more confusion.
I was committed to get to the bottom of this and set about learning more on this forum and many others. The bike revs free, no pipebang and no spooge. I ride at ft in QueenslandAustralia. Not a believer in JD jetting anymore or their advice given when contacted.
I hope this helps someone chasing the right settings for this bike and carb setup. Whats amazing to me is that people will put all that work into the Keihin, but not into the Mikuni and when both are sorted out run the same and would be less expensive to mod a slide and buy a few mains, pilots and a needle.
AJ, I respect your opinion on the Mik, in fact your jetting specs did work about the best I got it to work. I'm not sure how consistent your weather in Texas is and maybe that's why I've had a different experience than you.
Here in New England we get pretty wide swings in temp and humidity. While I could have the bike running perfectly it could then be a blubbering mess in the matter of a few hours. When we finally went to the Keihin this problem went away. Steve, I know the JD needles require different mains so maybe that's why you're ok with the m, that sounds pretty lean to me though so be careful if you do change away from the JD. Well AJ, amaze yourself no more. In my opinion, the Mikuni is a mismatch with this bike.
Keihin has been the carb of choice for KTM on their previous models with no problems. Here in Queensland Australia we get hot temps with humidity and the Mikuni was just too sensitive.
Hellion, cheers mate, I do intend on going to a main when swapping the needle to the N3CH needle. There was a post not to long ago by a mag or something that said once both these carbs are correctly jetted that neither are that temperamental with changes in elevation or temp. They even said the Keihin is very temperamental if not jetted right. I'll have to try and find it later.Getting Started with Jetting Engine condition In order to get good jetting results, the engine must be in good working order.
This includes: good reeds, clean air filter, good packing in the silencer, no leaking crank seals or other air leaks, and good top end condition. Rich and Lean Rich and lean in the context of jetting refers to the fuel:air ratio.
More fuel relative to the amount of air is richer. Less fuel to the amount of air is leaner. Jetting rich and lean is not the same as fuel ratio the ratio of gas:oil rich and lean. In fact, in the extreme, more oil actually means leaner jetting because there is less gas in the fuel mix.
At typical fuel ratios toyou can pretty much ignore fuel ratio variations in your jetting. Rich in a range makes the engine dull and slow to rev. Rich on a low throttle circuit, then lean as the throttle opens farther, produces a strong power surge or hit. More power is produced when you are slightly rich as opposed to slightly lean. If you set your jetting for perfectly clean operation with absolutely no stuttering under very light load such as very slowly rolling on the throttle on flat smooth conditions you are probably giving up a bit of power or grunt, especially at the low end.
Rich causes hard starting, plug fouling at low RPM and sputtering as the throttle is cracked opened.JD Jetting Motorcycle Jet Kit
Can cause randomly timed pipe bang when unburnt fuel burns in the expansion chamber. Main Circuit Lean causes a hesitation, then resuming when the throttle is rolled on.
Will cause engine to run hot and melt the piston if very lean. Rich causes sputtering and a dull sound and slow acceleration at WOT. Will increase fuel consumption. If the engine surges when the throttle is closed, the low speed circuits are lean. If the engine hangs at a certain rpm, then finally drops to normal idle, the low speed circuits are lean. If the engine stalls or comes close, then returns to idle, the low speed circuits are rich.
2017 KTM 250 exc Keihin carb jetting
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Try a 50 idle jet. The engine produces a maximum peak output power of Display per page. Ktm — knit to the next marker. Example: jet Putting the E clip towards the top leans the mixture because a thicker portion of the needle is blocking fuel flow through the needle.
The stock needle I have clearly looks like a 1, and the clymer manual has it listed as a 1 as well. Needle jet chart from the Mikuni catalog. It smokes the mik hands down but bike I guess was easier to ride with the mik because it didn't jerk you around. Keihin Needle Chart. Using the Kawasaki to Keihin Conversion Table and plugging those values into the Keihin's Profile Table we can determine we are looking at a needle with a 1 degree 15 minute taper, a 2.
Needle position. The further down the needle is, the later the main jet comes on and the leaner the mixture at that point. Do not waste your money on this piece of junk.
In the photo above, the jets, main jet holders, pilot air screws, needles and slides are shown. It also marked a switch to a Mikuni carb. Thats exactly right, you can't apply the Keihin codes to OEM special needles.
How it overlaps with the jet needle depends on the jet orifice inner diameter, air bleed holes and type of nozzle screen. Carburetor rebuild kit For other parts : 2A. Part way down page are needle specifications. Keihin Cable Adjuster.
It's straight from Keihin. The needle is broken into 3 main functions; Diameter, Length, Taper. I know the good needles have grooves for the clip so you have an idea of the distance you have set. Keihin Jets are sized in steps of 2 and 3. Keihin Carburetor Parts Diagram - Disclaimer: We never admit that the image is our image, the copyright is in the image owner, we only help our users to find the information they are looking for quickly.
Also the part that locks down the needle inside the diaphram assy. Rich Niches: BMW. The NECJ needle was the real difference maker for me.
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Thread starter Okiewan Start date Jun 19, Okiewan Admin Jun 19, Updated June 9, - Conversion Tables added.
Lets use the stock to KDX jet needle as an example. Kawasaki identifies the needle as an RN. Have a look at the image below and you can see how the part number is broken down into 4 sections as well as the parts of the needle. Each section of the code identifies a difference part of the jet needle's profile. I've color coded the the tables and diagrams to make it easier to identify the different parts and arrange the code in the proper order as you work through the example.
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This is absolutely remarkable! Thank you for taking out some of your scarce time to share this informative and educative article here.Remember Me? Advanced Search.
Results 1 to 8 of 8. Thread: Jet Needle Chart? I've been looking for an on-line Keihin jet needle chart that lists the stock NOZH needle in it for comparison purposes. Everyone in the jetting forum has great ideas for my bikes jetting but I would like to see how big a jump they are taking before I make any jumps myself! I tried carbparts. Maybe it's a KTM and not a Keihin? I thought I saw a link somewhere on this site during my travels here, but I can't for the life of me find it again!
Paul 60 y. James Dean's chart has sorta become the standard. If you look at some of his posts, I think he has his weblink under his signature. Good LucK! I would think that there is a free of charge chart out there somewhere by someone who wants to sell needles.
New Keihin Jetting Guide for Novice to Pro
I would buy from the company who puts together a good chart. Thanks Strick! To compare a needle with a straight diameter 2. Yes, it's a KTM part. Using a larger main jet by 2 steps keeps full throttle jetting close to unchanged when switching to these single taper needles. James www. It seems to be working, the "select" box needs to be checked to proceed. Sometimes the site goes down, try it again. I wouldn't have charged for this guide, but these needles are special order parts that start to add up in cost.
None of the manufacturers or aftermarket will give any details on them. I have had to buy and measure each needle and compare diameters and tapers to the standard Keihin needles.
It all adds up to a lot of time and expense to make a complete glossary. Your advantage is being able to see how the needles compare in profile and clip position before buying. Then I, and others, can usually help with suggestions, having ridden with them. I thought that these honda needles were double taper - but it appears to not be the case. Would a double taper needle help? The "S" at the end of the code adds a second taper at the start of the 1.
To reduce the spooge, lean the jetting carefully between the pilot jet, needle clip, or needle diameter.
The important part is to identify the throttle position giving rich jetting or sputter, and then work the range that needs adjustment.The site navigation utilizes arrow, enter, escape, and space bar key commands.
Up and Down arrows will open main level menus and toggle through sub tier links. Enter and space open menus and escape closes them as well. Tab will move on to the next part of the site rather than go through menu items. These guidelines should be followed when installing carburetors and other Keihin products:.
Carburetor Tuning. These guidelines should be followed when installing carburetors and other Keihin products: To avoid injury, carburetors should be installed when the engine is cold. Read the owners manual for your vehicle before installing any Keihin product to prevent any damage to the vehicle due to improper installation. Gasoline is extremely flammable and can be explosive under certain conditions. Installations should be done in a well-ventilated area. Installation of products in this catalog should be done by an experienced mechanic or service technician.
Keihin carburetors are only legal in California for racing vehicles, which may never be driven on public highways or waterways. Keihin carburetors are designed to be used with normal pump gasoline.
This may prevent the carburetor from functioning properly.