Needles for Keihin carburetors
Click here to go to my page with more about Keihin needles and my free spreadsheet decoding them.  Keihin needle jet inner hole diameters 2.9mm for PWK33-39, PWM38, PJ34-38, PE36, FCR28-41 2.6mm for PE26-28, PWK26-28, PE20-24 Heres what PWKs are often equipped with:  Needle Data for PJ34-38 PE35-38 PWK33-39 PWM38 from Jets R Us: The 48 series are for the large PWK carbs. The 46 series are for the smaller ones. This shows that you just use the last 3 letters of this code.  As an example look at the top left needle which is AEF. The first letter refers to the needle taper degrees/minutes, the second letter to the L1 length, the third letter to the diameter. So AEF has 1 degree 0 minutes (1.0 degrees), 38.15mm L1 distance, and 2.655mm needle diameter (at the straight section). CEJ has the degrees increased by 34 minutes (34/60=.57 degrees), same length, and diameter increased by .02mm for a leaner mixture at low throttle settings.     Here's Keihin's engineering drawing for the N3 series needles for the PWK33-39. They all have the same dual taper but vary in upper width.  I just lately came across the N3C data and don't conveniently have the room to squeeze it into the program so I put it at the bottom of the spreadsheet (starting at row 183 although the calculator doesn't access that data) and you'll have to enter any of their data in as a custom needle at one of the rows from 107 to 111. For all other 65mm needles you can follow instructions at my video to find their specs to enter into this spreadsheet. 
Analyzing the needle diameter graphs on the JD Jetting Spreadsheet I came up with these specs on the listed needles which are now programmed into the Keihin sheet on my jetting calculator. 
Needle Data for PE26-28 PWK26-28 from Jets R Us :  Needle Data for PE20-24 from Jets R Us : 
Keep in mind that the L1 length is not the length to the beginning of the taper but is the distance to where the taper will have a 2.515mm diameter. With needles that have a max diameter less than 2.515 then that L1 spot is actually imaginary, as if the taper kept extending upwards past the taper start. Needles with less than 2.515mm diameter: PE26-28, PWK26-28, and most needles for PE20-24mm. This was the explanation given to me by Jets-R-Us. Here's the needle code list for the rare needles for the PWK29:  Main jets and needles are also available from Sudco which is a preferred source for genuine Keihin parts. Just look at the main menu and then type in the page # you want in the upper left hand corner. These needles are for carbs PWK33-39, PJ34-38, PE36, PWM38 :  JD Needle Blues  Supposedly the experts at JD Jetting sell a custom made needle that is supposed to be ideal for the PWK carbs. But a person just consulted with me for better jetting and he measured it all and I figured out its angles and when I plugged its specs into my jetting calculator the result was really lean up till 3/4 slide opening because the length of it till the taper was about 6mm too long. So I found a needle that SUDCO sells that will give him perfect jetting according to my calculator. What is ironic about this bitter tale is that the spreadsheet by JD Jetting is what I used many years ago to find a better needle for my '89 Honda CR250. It was a good program but it only compared needles so you had to be experienced enough to know what part of the needle needs to be fatter or skinnier. About a year ago I asked if he could share his needle data with me since he no longer sells his spreadsheet and he said no and then broke off communication with me. I thought that was pretty stinky but by using his calculator I was able to logically derive the needed specs from a slew of needles he had programmed into his spreadsheet. He could of been nice and just gave them to me but instead he made me work for hours to get them. So now I have the full story. Any way here are the before and after jetting graphs. 
If you have any questions then just email me at 19jaguar75@gmail.com |