Taffy & LarryCO Jetting

56 replies to this topic
  • tctrailrider

Posted June 07, 2003 - 10:14 AM


I have tried various jetting combinations with DRR and EKN needles. MJ from 160 to 175, PJ from 38 to 45, clips 2-3-4. The bike has allways run well, no plug problems, easy starting. My only complaint with previous combinations is not enough jump off the bottom. I ride single track at about 500 feet. Most riding is second gear below 1/2 throttle. I ordered the leaner jets this week and just finished testing. I have been running EKN3 160MJ and 45PJ.
Started today with 155MJ EKN4 38PJ PAS65. Ran better than ever. 4th gear WOT, let off the throttle and get one or two loud bangs. Turned out the PAS a little, the bangs went away but the acceleration down low was not as good. PAS to 60 and 35PJ. The acceleration down low is just awsome. Motor pitch is higher but it doesn't seem to lean. Motor is running hotter, I can feel it from the pipe. I still get one or two bangs letting off the throttle 4th gear WOT, and from idle if I wick the throttle it will stumple or stall. Would like to get rid of the bangs and the stumble. Can anyone bring me home on these issues. Other mods are in my signature. Thanks

I just turned out the fuel screw a bit and the stumble went away. I also went to a 160MAJ today.

  • Taffy

Posted June 07, 2003 - 11:07 AM


jesus this one's a maze.

ok, i would say your MJ is fine. you must richen the bottom end by going back to a 45 PAS setting then take the PS out to two turns from all-in. so we are richening 1/4 throttle. try some snap wheelie tests at 1, 1.5, 2 turns out on the PS.

then lower the needle in a second test and your idle stumble may go away a bit.

if not your APJ isn't functioning correctly.

you don't mention howmany turns out the PS is now also you don't mention a pipe?


  • tctrailrider

Posted June 07, 2003 - 11:41 AM


I am running the stock US pipe with a Baja Designs Vor tip. After my post I checked the fuel screw, out one turn. I went out to 1 1/2 and got rid of the stumble off idle. So the current issue is the Bang or two on decel. I assume this is a rich condition on the Pilot circuit. If I go in on the PAS won't this make it richer? I know that I am higher on the PAS ratio than suggested for the 35PJ. The ratio's make me think I should go in on PAS and the Bang makes me think I should go out. There is a little concern with going to lean and spending $$$$.

  • tctrailrider

Posted June 07, 2003 - 12:12 PM


Just took another test ride with the fuel screw out 1 1/2 and the stumble off idle is gone, and the pipe temperature seems lower. Still get the bangs on decel but not terrible. I have a long gradual uphill road nearby and things are smooth and powerful all through the throttle settings. I jumped off the pavement on a short dirt road and did some 2nd gear messing around. From low RPM's the throttle response is wonderful. From down low it lites up like a two stroke. All other jetting tests the motor had a deeper sound and slower response. Think I am very close. If the rain holds off tomorrow it will get a test in the woods.

  • tctrailrider

Posted June 07, 2003 - 01:20 PM


Did some more testing and here is where I ended up.
155MJ, 160MAJ, EKN5, 35PJ, PAS45 (1/4 turn out) 1 1/2 on the fuel screw.
WOW, this thing rips
I went in on the PAJ which seemed backwards to me and the Bang went away and I did not loose anything on the acceleration. Raised needle from 4 to 5. I was certain this was a waste of time, and a little flat spot at about 1/3 throttle went away. I am at about 500 feet and 65 degrees today. Plan on a trail test tomorrow. If it runs in the woods like it did around the house my jetting days are over. I had a WR400 and now the 426. Numerous jetting attempts with some results. I allways stuck close to the more conventional jettings (JD) etc. Your lean jets and rich needle settings seemed pretty distant to me, worked for some and not for others. Glad I like to tinker and decided to try them. The difference is huge, had no idea this bike, with a baffle would run like this. LarryCO if you read this, I also followed your lead when you came down to altitude. Thank you,

  • larsonsenza

Posted June 07, 2003 - 04:24 PM


After taking your bike out in the trails with new settings, can you please report on how it is running and if you have it dialed in. I ride in Gaylord, MI and am thinking about trying your settings. Thanks

  • Pooley

Posted June 08, 2003 - 06:58 AM


Ditto on the update. I just ordered the jets to do the same thing this week. I live in Canton and do many of the CCC events so our terrain, temps and elevation should be nearly identical. The only thing I dont have is the #35 pilot, I was going to start with the #38.

  • Taffy

Posted June 08, 2003 - 08:44 AM



on the money then hey :) don't lift a needle just to get rid of a pop or bang go by how it feels.

do some snap wheelie tests in first and second with adjustments to your PS. try 1.5, 2, 2.5 turns and see.

i think that clip five is too high and if the PS test goes the way i think it will then you'll need a larger PJ (38 with #60 PA)then drop that bloody needle back in the hole.

so what you are doing is saying too lean low so lifted needle and i'm saying let the PS tell the truth and it should say "we need 38PJ/60PAS and the nedle back down" could be wrong and don't change what you feel to suit me or you but try to be constructive and equal in your deliberations.

that's why i won't tell you where i think your PS will end up-you tell me.


  • tctrailrider

Posted June 08, 2003 - 11:10 AM


Lots of rain today, did not get to the woods. Did a little testing around the house. The jetting I ended up with yesterday, 155MJ, 160MAJ, 35PJ, 45PAS, EKN5. Did snap wheelie tests changing the Fuel Screw 1 1/2, 2, 2 1/2. It seemed the best at 1 1/2. When I started it cold today, started good, idle went high after 5 seconds of choke, shut off choke and idled fine. Constant speed at 1/8 throttle some surging.
Changed PJ to 38, PAS to 60. Snap wheelie tests and ended up at 1 1/4 on FS. No bang on decel and the surge at 1/8 is now hard to detect. On acceleration the two setups are so close I could go either way. Will stay with the 38, less surging and no bang.
Tried clip 4 and there is a definate flat spot at around 1/4 throttle, clip 5 much better, seems to accelerate stronger all the way through. On a long gradual hill slowly accelerating there is a little miss at about 1/4 throttle. It runs right through it. My guess is that this is the transition from straight to taper. Tomorrow I will get a small washer to try clip 4 1/2. Its very close to WONDERFUL.

  • Taffy

Posted June 08, 2003 - 10:54 PM


i'd like you to try a 152MJ and then a 158MJ in that order and try and sort which is the best.


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  • LarryCO

Posted June 09, 2003 - 05:25 AM


And while you're at it, take off that vortip and redo all tests...so I dont have to go through it all myself! :D Oh wait...that's half the fun! Never mind...

Glad to hear things are sorting out for ya...good stuff... :)


  • tctrailrider

Posted June 09, 2003 - 12:32 PM


So excited about this I took the afternoon off to rejet.
Put in the 152MJ. Ran terrible, 1/8 to 1/3 throttle, missing, sucking, no power.
158MJ better than the 152 but not good, big misses.
Put the 155 back in and raised the needle to 6, not good, would hardly run over 1/8 throttle.
Changed needle to clip 4 with a washer, that would be (I think) ELN5. Very small miss at about 1/4 throttle, wonderful above that, now very close. On WOT to decel, one loud bang. I went out a touch on PAS and I think I have it.
The bang in gone. On a long gradual up hill with slow throttle increase its good all through it. I ended up at 38PJ, PAS out just over 1/2, FS 1 1/4, 160MAJ, 155MJ, ELN5.
Don't know if I am spot on, but its very close, much better than all other attempts.
During this process several times I thought I was lean, or rich at different throttle positions and jetting changes proved I was wrong most of the time. On a 2 stroke the deep sound is rich, on this I found it could be lean. Also at lower throttle settings, above 1/8 the MJ is huge. It effects jetting far lower than I ever thought. At approx. 1/4 throttle 155MJ good and the 153 and 158 were terrible.
So I would like to be done with this but I will follow the commands of the Master. Taffy where would you like me to go.
Thanks, Denny

  • Taffy

Posted June 09, 2003 - 01:23 PM


those MJ tests shouldn't have come back as black and white answers IMHO. they should all have been in the ball park or, as i hoped, one should have been bad and the other as good as the 155MJ. i was on about flat out here yes?

have any of the tests you've written up about been written in the wrong order?

the thing is the needle is shouting too rich and now you have the 38PJ in you can afford to try the needle a clip lower.

i'm talking clip 3 and turn PS out to two turns as you do it. then if at all succesful snap wheelie tests with .5 turn in and out to see.

you must expect a little popping and banging as long as it sounds like a muffled fart they're ok.

just check the headers are tight and your mid section connection etc. no air leaks.

i can usually put my finger on it but this one is tough. like i said mr 2-smoke don't get het up over a bit of popping and banging.

if you've had enough and your happy withit then you stop. and well done coz you've done really well. you've tested things and had a crack at it so good onya!

BTW we brits will be snuck up in bed doing zeds by the time you answer this so don't rush!!!!


  • tctrailrider

Posted June 09, 2003 - 03:43 PM


After dinner I went out for a ride. There was more surging at approx. 1/8 and more missing at 1/4, not terrible but more than earlier. Removed needle washer and set at EKN4. Turned FS in and out without much change. Went back to 35PJ, in and out on fuel screw and PAS, back to 38PJ, in and out on both.
With either PJ the fuel screw seems to effect the very bottom only, if in to far it will stumble or stall off idle.
With 35 PJ and PAS 1/4 bottom revs fast with some missing around 1/4 throttle.
38PJ 1/2 PAS good on bottom and less missing around 1/4. With either PJ if I go in on PAS the bottom seems good but more missing near 1/4. If I go out on PAS the acceleration is blunted.
Over 1/4 throttle the acceleration is great, so the needle and main seem perfect. With 38PJ, 60PAS and 1 1/2 FS, EKN4, 155MJ and 160MAJ, so far is the best. The issues I would like to correct are a little surging at about 1/8 and some little misses around 1/4. I think its the transition from pilot to needle. If I were to go up a long gradual hill, 3rd gear and slowly accelerate. Start clean, minor surging around 1/8, little studder or miss around 1/4 and then pure and clean to WOT. In real riding conditions I either am rolling on or off the throttle and it goes through these issues allmost without notice, its good as is just not perfect. Thanks, Denny

  • Taffy

Posted June 09, 2003 - 09:30 PM


it may be that the PJ is having to do extra work because the needle straight is too fat causing leanness when moving off and a hesitancy. so a E*M needle and either stay at 38PJ or go to 40PJ in a second test.

if as i suspect, you didn't have that 1/8 throttle problem until you dropped the needle it probably means you need the EMM needle.


  • tctrailrider

Posted June 10, 2003 - 05:27 AM


Have to order jets so further tests will be a day or two. Ordering E_P, E_M and a 40 PJ. This will give me one step on each side of the EKN on the straight. Thanks for the help, will keep you posted.

  • tctrailrider

Posted June 11, 2003 - 01:57 PM


Received my jets today. Ordered yesterday at 11.00AM from sudco, two needles and a pilot. $20.06 plus $30.39 shipping, one day air, but they were here when I got home from work. Got a 40PJ, EMP and EMM. Wanted needles one each way on the straight from EKM. Put in EMM4 and the surging and studders at 1/8 were terrible, also ran bad above that. I then realized I was to rich on the straight ( I was confident it was to lean). Went to EMP4 better but not good. Clip 3 better. Changed back to EKN on 3, pretty good, went from 155 to 158 on MJ, better, clip 2 better yet, dropped to 35PJ, 45PAS and its smokin. Ended up at
35PJ, 45PAS(1/4 turn out), EKN2, MAJ160, MJ158, and two turns out on fuel screw.
If its not dead on its within a hair. Throttle response is crisp and smooth all through it, some hit at approx. 1/3 throttle. On decel no popping or bangs. Its wonderful. Lower RPM's it jumps. That was my goal, more on the lower end, its also better everyplace else.
The jetting of these is a chore. One clip position can mean alot, one anything can. I was on EKN5 and very close and ended up on EKN2. The different circuits overlaping and effecting the others is complicated. To tell rich from lean below 1/3 throttle is difficult, and I was wrong most of the time. Holy sh--, my head aches. Thanks for all of your help. Us squatters appreciate you pioneers clearing the way.

  • Guest_Guest_*

Posted June 12, 2003 - 11:16 AM


Great job :thumbsup:I'm going to copy your work as a starting point when the 496 comes thats replacing my E silencer. anyway back to the top :)

  • Taffy

Posted June 12, 2003 - 01:25 PM



well done. there's those that talk...

on the 6th you said the needle was better when lifted and on the 7th onward i was saying everything pointed to dropping the needle.

imagine what it was like for me and JD? luckily i didn't give two-hoots what it sounded or read like on paper. it had to perform better.

i high needle gives a surging feeling like the kill switch is being flicked on and off by an annoying little brother or similar. that means you're at least two clips too rich.

by the way your EKN (put EKM in your post-you may wish to change it for others to benifit)is so far down the hole and one more clip (clip 1) and the EMM WILL become valid. as you read in jetting Qs, when a needle goes a long way down the hole the needle width could be 'thinned out'.

suddenly you're only jetting difference between yours and mine is the +8 of the pipe and i've always said that a pipe is worth +8!!!!

well done again.


  • tctrailrider

Posted June 12, 2003 - 03:10 PM


Thanks for the help. I suspect that I will become bored and try very minor changes (one clip, or one richer or leaner on the straight, etc.) Just to see if there is anything left in there. I went out for another test ride tonight. Started first kick, choke off 30 seconds, idled fine. Eased it out of the neighborhood 1/4 mile and from 1/8 to 1/2 in ran terrible, studders and missing. Kept riding and after about 5 minutes, good and warm, it was wonderful. Rode another 10 minutes and this thing flies, the lower end hit is explosive. My rear tire budget will need an increase X2. I wanted to end up at EKN3, 38PJ and 155 MJ. It took me about 15 or 20 different settings to get the feel and start to understand the issues and co-mingling of the jets. 1/4 throttle issue can be a MJ problem, the answer may be far from the logical jet. Its fun when it works out but the process is a pain in the ass. I also found that my EKN needle is the aluminum looking brand. The needles I got from Sudco are brass. When holding the EKN, aluminum and EMM, brass needles together, the the N is thicker on the straight as expected, but the distance from the taper to the clips was the same. So when changing brands of needles there may be some variation. Also previous jetting was kick and go, new setup needs to be up to temperature, and then hang on. Taffy, thanks for stepping out of the box, and going where no man had gone before. Your off the wall jetting is GOOD stuff.


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