[ May 01, 2002: Message edited by: Dirtnut ]


I don't question your jetting knowledge but you are on a different continent and your jetting is so different than a lot of ours.


If you hear popping, you are probably already too lean. Leaning it further would make it worse. I'm out of my element here, I ride a 250F but a 175 sounds pretty big for a 426.

You say when you open the throttle you get popping. Unless the popping occurs when you are over say 2/3 of the throttle, the needle is playing a bigger part in your jetting than the main is. Is it possible that the popping is as you roll through the 1/4 to 2/3 throttle range. If so, try raising the needle one or probably even two clip positions. If this helps, you might be able to back way down on your main.

Again, I'm on a 250F but even the pilot sounds high. On the 250F forum is a 'Jetting 101' post that might help. Also, in the manual there are three sections about the carb, under 'Inspection/Adjustment', 'Engine/Carb', and the last chapter 'Tuning'.

Taffy, when you get to this, it seems from reading the 426F forums, that the main jet on the 426 has limited effectiveness outside a central range (maybe 160 to 175?). I think you reported once that going down to a 155(?) didn't make much difference from the 160(?) you preferred. And people end up with huge variations in mains for the same needle, in one case from 158 to 178(?). Can it be that people are riding these bikes down low, I know they can do that because I hear A and B riders at the local track going fast at low RPMs, and never actually run on the main. Could the range be limited because of the MJ/MAJ ratio? Just curious.

Good Luck Dirt,



you're giving jetting advice again without having been there. calm down.

everyone who is running low # has been high and decided leaner is better. but none of the rich blokes have ever run them lean.

it's an insult to say that we live a long way from each other so the jetting has got to be hugely different. jetting is to do with the amount of power and it's curve. as long as i can tell the difference two sizes of carb make i (and JD) have no problem helping any model.

as i've said countless times people who copy my jetting or go withthe numbers i recommend are not experintin, they're just happy that it's quicker and sweeter etc.

now that's not my fault is it. the high MJ numbers are wrong. if people want to go that way then f*** 'em!

i've spent enough time helping them. if this sounds big headed then fine but i've lead the whole website to this point. i don't see anyone else with anything like my practical knowledge.

i'm tired of pushing pushing pushing and bryan hasn't answered my request to archive the Jetting Qs. that means more of this.

i can't convert the whole bloody internet.



I didn't try to insult you it is just your jetting specs are so far away from a lot of others. I do appreciate your help and I am willing to give your jettings a try. I have tried everything else.

To all those who replied thank you.

Well all that soot is telling you it's Very Rich

You maybe pulling in some air somewhere else like the carb/intake boot?

You prolly wouldn't notice it so much with richer setting.

Just my 2 cents? :)

Lord help us, Taffy is the only one with any real practical knowledge. :) I'm getting real tired of the "they wouldn't listen to me so f*** 'em" attitude. The world apparently doesn't appreciate Taffy to the degree that he deems is appropriate. Even this site's admins don't show him proper respect in his eyes. Jeez, he actually entertains the notion of controlling "the whole bloody internet".

Mark, I think you have introduced an intriguing insite that might actually have merit. Some of us are still trying to learn more about how carb jetting works. Anything that would help explain some of the varying reports would be a breakthrough development in my estimation, if it bears out. And if it doesn't bear out, well we keep trying don't we?

Sadly, I have long since given up the temptation to post any contribution pertaining to the subject of jetting on TT. I'm no expert and so I keep my experiences to myself and only read without commenting. However, I refuse to have my jetting prescribed to me as I feel very strongly that in the long run we are better off for knowing what we know and knowing how to apply it. Besides, I detest arrogance. If I thought I could only keep my bike running by consulting Taffy everytime the weather changed, I would just leave it in a ditch somewhere.

So, the next time some jacka$$ tries to piss on someone's head for speaking out, well just be sure to notice who's the one trying to help and who's the one doing all the pissing.


I still think that popping while opening the throttle is because you are lean. But you are too rich most places. Your main and pilot both seem large, I alluded to both in my earlier post. The reason I was trying to get you to pinpoint where it was is because the needle is the only likely place you could be lean.

Taffy is right. These bikes come way too rich. Even after opening up the airbox and the pipe, they are still way too rich. You will find a snappier bike hidden somewhere under the too rich condition. You need to isolate the lean, if there is one, and then clean up your jetting. The Taffy standard is close to the JD standard and can be found on various posts. Or you can look at his signature line. That would be an excellent place to start.


I am a recent WR250F owner, a little over a year, and I am no expert. I post often (and as Taffy points out, am often wrong). I am getting a reasonable education from him and a few others. I see my job here not as offering expert advice but leading people to logical conclusions about basic jetting, not tuning jetting, just fixing obvious problems. Taffy often steps in behind me and cleans up my mess. I also encourage people to get started with jetting by pointing out how to get into the carb, a little about how it works, and a little about what symptoms indicate what corrections.

When I first found the forum, I found the 'bible' for jetting tuning, 'Jetting Q's', a little intimidating. I needed to fix a problem, a basic problem way beneath the level of detail Taffy was working on. You know, which clip position instead of where the taper should start, kind of questions. I didn't think Taffy would be interested in telling me whether I needed to pull the carb to do this or could do it on the bike. Since then, I have been in the carb dozens of times and tried more combinations of jets and needles than I have had rides since I started. I'm just learning now.

I am trying to put a friendlier face, or more particularly a more tutorial atmosphere, on jetting. I hope this encourages people to get started on theirs.

All that being said, there are several experts on this forum, Taffy and JD being the two I have paid the most attention to. They perform extremely valuable services to this forum (and others like the WR400, YZ400, DRZ, etc.) and would be sorely missed. Taffy has put some people, like yourself, off. Some of it is cultural (speaking of which, I don't understand some of his coloquialisms and I've worked in England and Scotland). Some of it is probably his frustration. It doesn't bother me a bit to answer the same questions, with lots of typing, time and again, but Taffy feels with some justification that people should have searched for answers and found them instead of reposting the same thing. My only criticism of him is that many people can read "Jetting Q's" but are novice enough that they can't follow it and therefore don't get through to the conclusions. A recap or Cliff notes version would be useful.

Anyway, good luck,


Mark -

>people can read "Jetting Q's" but are novice >enough that they can't follow it and therefore >don't get through to the conclusions.

I have to say I've read about 1/2 of the Jetting Q's and it's over my head. However Mark thanks to you Jetting 101 it gave the initiative to swap out the MJ this last weekend. (amazing tranformation to my bike)

I as a Newbie appreciate "ALL" the input I can get weather it be redundant or not.

I do wonder about Taffy being "Over There" what there fuel is like. What elevation is etc. How his setting mite cause a bike to act different here in the hot humid south?

PS maybe a cliff notes version would be the way to go. :)

Thanks to all


You downplay the significance of your willingness to contribute to other's successes at the expense of your time and trouble. The level of your experience/inexperience is evident enough. That is not the point.

While you may feel that Taffy is a primary source of modern day carb jetting knowledge realize that his experiential timeline precedes yours by not very much. Read some of his posts from this time last year. There has been much experiment and development work done around jetting on this site and elsewhere and Taffy has benefited from others' guidance just as have you and I.

Read the entire "Book of Taffy" and you will find wild variances in his prescribed jetting parameters (I don't think anyone has gone further to the rich side on the pilot and swearing all the time that nobody would listen to his good sense). He scoffed at the original BK mod and preached the complete elimination of the APJ. Now he has his own APJ mod. Taffy has arrived at workable jetting numbers for his carb through trial and error. Yet, if you listen to him today you would think he invented the damn thing.

I have no doubt that Taffy has learned some things from his endless "tests". However, his base of experience and advice does not warrant his ill treatment of others. And I'm not convinced that his is the ultimate solution set to the problem which encompasses all variables.

What I have learned most from all of this (and you have said it yourself) is that in order to achieve jetting prowess you must get your own hands in it. And it comes down to the simplicity of this: Your posts encourage people to learn for themselves. Taffy's posts discourage people from trying to comprehend and are not cryptic or enigmatic by accident.

Don't kid yourself about the graciousness with which he dispatches his brilliance to so humble an apprentice as yourself. Noone would "sorely" miss Taffy's presence here more than Taffy himself.

:D I tried BOTH ways, My bike arrived with a 175 is fair to say it ran like Sick Cammel!

Black exhaust, lots of stalling, bog when you gassed it etc etc......, I've also tried it lean....much much crisper, more power, more miles to the gallon, more drive....less bog in fact there is now ZERO bog off idle, if I gas it, it goes!, I know two bikes are not identical, but I just cannot see how you guy's can run a 180 and it runs fine, I'd need to call a chimny sweep every week to keep the can clean ! :)

All I can say is try the leaner method, Taffy has explained it to me in detail, whilst I'll never be as clued up as he is, at least I can understand the relationship between all the circuits in the carb and what altering each one theory :D

it works for me!

do you ever shut up :)



My 2 cents.

My wr400-99 runs rings around 02 426's with $650 ozzie $ exhaust pipes. i modified my pipe my self.

I let the others have a ride on my bike & they can't beleave how much more powerfuler my 400 is compaired to there 426's.

This I owe to you.

Iwould of never got the bike to run as good as it does without your jetting


I have read many archives on jetting & I am still learning, but now I'm starting to put it all together.

I find it amazeing that somebody on the other side of the planet can help me with jetting problems here in Australia.

I'm amazed at the advise the bike shops give on jetting, includeing yamaha shops.

They all tell you to go richer everywhere especially on the mains. They tell you that for every 5 you go down on the mains you loose 1 hp.

What crap.

Who can ride a 400 or 426 wide open in the bush anyway.

To finish off,thanks for shareing your knowledge.

Ok everyone

I did not post this to start a bashing post among us blue brothers. I don't feel this is necessary. I have read for hours on the jetting of these yammies. I just wanted to know if anyone was experiancing the same as me. I have had the pilot down to 38 and the main down to a 168. My bike will not run with the jetting that lean. However I did not change the needle. I have been jetting two stroke snowmobiles for years and I am not ignorant to jetting. These pumper carbs are totally different and more jetting circuits. One thing that I have experienced is that on a flatside card the needle is more critical.

I am going to try Taffy's jetting now I have to find the jets he is recomending. I will bet that most Yamaha dealers will not stock these jets.

Good luck to me

I got the parts I needed for "Taffy Jetting" at Sudco

wow, this is a war. form my point i got this to say, looking At all tyhe differend ajustments that taffy has made(sh#t i don't know what half of those are) i bet the poping pople say they have is made up with those ajustments so his bike runs great. for now i niether the time or money to deal with it. maybe after college( and i have a real job) i can look into it. i would really like to see what jeting specs Tim Ferrt runs in his bike. hell if you bike runs good too you, leave it alone.

neWRiver....why the BIG downer on Taffy, sure he is a might abrasive at what, it doesnt mean he doesnt know his onions now does it????

Every time I see you post lately it is to knock Taffy, down with Taff, oh he's an ar$e, he lives on different continent, how can he be right, well his advice worked for me, have you tried it or have you "Cut off your nose to spite your face"?

Taffy said , so there is no way I'll try that.

For someone that is very quick to diss Taffy for his manner, you are NOT exactly the smooth urbane type yourself, your constant whineing about Taffy's post are getting tedious, almost as tedious as you claim Taffy's blunt speaking to be, In this latest round, you were not even in the discussion, you seem to have gone out of your way to join in, if you find him that objectionable then dont post on the same threads.

Taff has helped (in his own blunt way )more people on this forum than you so where do you get off?

Sure I'm from the UK as well, dont mean sh1t, I know when a blokes an ar$e and when he's not stop acting like one and quit bleating!


Are you now "inviting" me into the discussion (i.e. do you want those questions answered) or are you also telling me to shut up (i.e. "quit bleating")? :)

Nevermind, it doesn't matter. Please note that I would not be as presumptious as to counsel either you or Taffy as to when you should speak or when you should shut up. I leave that to your discretion. I am merely stating my opinions (much as you have just done). As far as where I "get off", well I just follow Taffy's lead and get off wherever I damn well please.

You may well find my posts objectionable. But please, they are nowhere near "constant" or even remotely "as tedious" as some others. :D


although i did answer directly your question in your second post the rest was me ranting.

it was aimed past you at the open air...


Sorry Boyz,

Didn't realize that I was opening a can of worms with this post. I was just curious about going bigger. It sounds rather simplistic, and it is, but I figured more gas to the piston the faster it would go. I have the wr timing, the bike breathes well with the T4 complete exhaust system and lid removed, and I was just wanting an edge over my buddy. I was just concerned about the possibility of squirting too much gas in there and causing valve damage. Seems nobody responded to that concern.

Thanks for all the interest though.

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