Jetting Mikuni TM carburetors0) Scroll down to row 171 to get the equivalent 4/042 main jet # to put at F5 if your TM has a N100/604 series main jet. These series of TM carbs come with N100/604 main jets: TM33-8012, TM36-68, TM40-6. This calculator requires the N100/604 #. Other versions of the TM come with 4/042 jets. 1) At row 26 you enter the needle data (the straight section length and needle diameter every 10mm). 2) Then enter "S" for single taper, or "D" for dual taper at A28. (You can see in column D below row 54 if there is one or two angles listed for each needle.) 3) Next enter the length of the first needle taper at A30 if it is a dual tapered needle. You can find that length in the needle data section. 4) Enter at C30 the millimeters the slide is open when the start of the needle taper is at the top of the narrow section of its jet. You can use the method described on the previous page or enter the needed info at A35 and B35 and then put the # that results at C36 into C30. The needle base height of A35 is the distance from the lowest part of the slide up to where the needle clip rests. 5) Then you can manually transfer the computed numbers at row 31 (C to I) up to row 12 (C31 to C12, D31 to D12, etc) or if your spreadsheet software handles macros just click onto the macro button that is labeled "transfer #'s" at J31. The one at J28 is for when your beginning needle taper is at the top of the narrow part of the needle jet when the slide is close to being 3/16 open (which is halfway between 1/8th and 1/4). The macro button at J31 is for when you enter at C30 the distance the slide is open when the taper start is at the top of the needle jet. 6) Then look at the red graph results to see if the it is above or below the 1.00 line at 7/8 slide opening. If the correct main jet size for this carb is unknown then you change the main jet size till the red graph is at 1.0. If you know the main jet size and it gives a chocolate brown colored plug then put the number from G3 into G2 to correct the graph height. 7) If you want to raise or lower the graph beginning then change the slide cutaway millimeters at G5 to raise or lower the beginning section of the red graph to come closer to the 1.0 level. 8) Then notice the graph at 1/2 slide opening and if it is above 1.00 then you need a needle with a shallower 1st taper angle, or if it is below 1.00 then look for a larger angled needle. Above 1.0 is too rich, and below it is too lean. To store the results of any needle just click onto any of the "Record Results" macro buttons before entering data for a different needle. The graph for the recorded needle will also show. So you can see the graph for 4 needles at once after recording for 4 different needles. To clear out all previous records just clisk onto the ERASE RECORDS macro button. Re-record this spreadsheet with all of your data in it. 
The normal #5 series of standard Mikuni needles are suitable for the TM34, and the #6 series is good for the TM36 to TM38 non-pumper carbs. Listings of all the standard Mikuni needles: Jets R Us (scroll down half way), and NicheCycle. (The #5 and #6 data on my spreadsheet is even better because it has corrections for obvious errors in copying.) Each MIKUNI NEEDLE is identified by the letters and numbers stamped on them. Example: 6FH7 6 is the length, which in this case is more than 60mm but less than 70mm F is the top taper, A-E having less taper H is the bottom taper (sometimes the NEEDLE has only one letter, in that case it refers to a single taper) 7 is a mfg code not normally used in tuning. TM NEEDLES TM24, TM28, TM32, TM34: 5D120 5FL14 5DP7 5F3 5L1 5F12 (lean --> rich) $7.04 TM24, TM28, TM32, TM34: 5DL31 5DP10 5DP39 5E75 5EP6 5F21 5FP17 5FP96 5J11 5N13 $7.04 TM33-8012 PUMPER CARB: J8-5FP96-3 $7.04 TM38 FLATSLIDE: 6DH2 6F9 6DH3 6l1 6DP1 6DH4 6DH7 6DH8 6FL14 6F15 (lean --> rich) $7.04 TM38 FLATSLIDE: 6DJ30 6DP4 6DP17 6F4 6F5 6F8 6F16 6F21 6FJ6 6FJ40 6FJ41 6FL25 6J1 6FM46 6N1 $7.04 TM36 TM38, 39 + 41 PRO SERIES: 6FJ41, 6FM46, 6FJ40, 6DP4 $7.04   Here's what Mikuni TM's typically are equipped with. 
This pdf explains the difference between the 4/042 series and the N100/604 main jet series. The following is additional info that doesn't really apply here since I don't have the needle data for the TMS or TMX carbs. But I don't want to lose this info in case in the future I get the needed data. If you have any of these needles you don't need then pease send them to me to measure.  TMX + TMS needles:   TMS/TMX Needles from Jets-R-Us: EARLY STYLE TMX35 FLATSLIDE: 6EN11-(52/53/54/55/56/57/58) $7.04 EARLY STYLE TMX38 FLATSLIDE: 6EJ12-(53/54/55/56/57/58/59/60) $7.04 TMS38-77, 78 125cc: 6GDY12-(56/57/59) $7.04 TMS38-77, 78 250cc: 6DGY04-(54/55/56/57/58/59/60) $7.04 TMS 38-78: 6CEM(01/02/03/04/05) $12.04 Example Mikuni TMS needle: 6DEY26-66 The first 6 is the length, which in this case is more than 60mm but less than 70mm The -66 translates to the straight part of the needle. Divide it by 100 and add to 2 so that 66 = 2.66mm in diameter. And 6DEY26-67 = 2.67mm dia. Other options: 6DEY27-66 is a 1/2 clip richer than a 6DEY26-66 Letters DEY indicate triple taper needle. D=1 degree taper, E=1.25 degree, Y=6.25 degree. A=0.25 degrees and increase by .25 degrees per letter increase. One letter indicates a single taper needle, and two letters indicates two tapers. |