YZF pipe on a 2000 WR - Jetting

I'm going to put a YZF pipe on a my 2000 WR.

It's got airbox top off and YZF throttle stop.

So far stock jetting works good.

Fuel screw 2 turns out. Starts first kick

Bogs and stalls sometimes. Seems to clear up when motor is hot. Worse in the hot weather. Maybe it's rich in the pilot in the hot weather?

Also has a little midrange surge w' steady throttle on road in the cold <40deg weather.

Maybe running a touch lean midrange in the cold?

Should I consider rejetting with the YZF pipe, or just put in on and go.

If jetting is suggested, where would be a good place to start. I was thinking of a clip down on the needle.

What do you guys think?


I hesitate to respond because I ride a 426, your jetting will be a little different, but there have been a slew of posts over the years about guys on 400s running "E" taper needles, or basically a stock YZ 426 needle. I don't recall one where the owner didn't prefer the "E" taper needle.

Also has a little midrange surge w' steady throttle on road in the cold <40deg weather.

Maybe running a touch lean midrange in the cold?

That makes sense, and is exactly what the stock "D" taper needle would do. I would only be guessing at the pilot and main so I won't go there.

Here is a Yamaha PN, off the '00 YZ fiche, that would be a good one to try I think:


It is an EKP needle, and fourth clip would be a good starting point.

You may also search for some of the older WR 400 jetting posts, if you find TTalk user James Dean you have hit paydirt. He is a jetting savant of some kind, and used to have a WR 400. I think he rides an orange bike now, you may try finding him on the orange side and send him a PM.


You might want to try an EKN needle in #3.

Okay, I guess I need to get my hands on theese needles as well as a couple of mains, I already have a 45 pilot.

I presume the EKN is different than an EKP?

Which one is leaner? Is the EKN the stock needle in the bike now?

Gonna be jettin' soon. Think I'll tap the carb body for the BK mod also.

Guess that will require fattening up the pilot a little. No?


When I cut the grey wire I noticed the steady/mid throttle surge thing went away.. It was most noticeable on the road like you mentioned.

Let me know how the yz pipe works out. I have the wr426 pipe on my 2000, but I think its the same pipe except for the stainless exterior.


The stock WR 400 needle is, I believe, a DTM. I could be mistaken ‘bout that...

Each letter is a different specification. The first is the needle’s taper angle, second is the clip position, last is the straight diameter, and each single change in the letter is one step richer or leaner (the letters O and I are not used).

So an EKP is identical to an EKN except it is one size leaner on the straight diameter (N to P, remember there is no O), which governs mixture just off the pilot, before the slide pulls the needle up onto the taper.

To explain the middle letter I’ll compare a stock ’01 YZ needle, EJP, simply put it is ½ clip richer than an EKP but identical in every other way.

Changing the taper just one size, from D to E, is a bit more drastic, and has a wholesale affect at just about any throttle position just off idle. What is happening with the steeper taper angle is the needle is getting smaller more quickly, as you open the throttle the rate of change in mixture is greater, so just saying an E taper is richer than a D is oversimplifying the change IMO.

With the less restrictive setup you have now vs. stock, I think you will notice a big improvement over stock w/ just about any E taper you try.

Since you are in NJ, and it is getting cooler, the needle Toyz suggests may work better than the one I originally did.

Here is the PN for an EKN:


As for the accelerator pump mod requiring a fatter pilot, I’d say not necessarily. Ultimately you’d like to jet the bike with the accelerator pump off. I guess what I’m saying is that with a limited (or eliminated) accelerator pump you may want a richer pilot, but only because the pump was masking the fact that you always had an overly lean pilot.

Hope this helps.

Help? Yes. Thanks a lot!

A jettin' I will go....

I'll post results


I run a 400 and I run a "D" taper needle, not the stock (UK) DXM but a DTM, with the right jetting (as per Taffy)it seems to have a bit more bottom end then the "E", I also run the YZ end can the rest of my jetting is as follows





Pilot screw 1.5 turns out and the dreaded APJ less than o.5 sec's

it'll wheelie off the throttle in 3rd and with the clutch in 5th loads of MPG and starts first kick hot cold, upside down etc.....I NEVER use the hot start or foul plugs :)

These settings worked out with Taff and they work Grrreeaaattt ! :D

Thanks, I presume yr WR is a 2000?

What clip do you run on that DTM needle.


Man I really need to rejet now.

Rode Y'day in 35 deg weather.

Usually when I pull the Vortip the bike pulls quite a bit harder. Y'day noticed no difference at all.

Last night put YZ can on, now it pulls okay off idle but everywhere above that it is just flat. Definite loss of power and a little backfiring on decel.

Am waiting for a shipment of "E" needles, but am thinking of just raising the needle one clip.

Do you guys think that would hold me over till the "E"'s arrive?

Lastly does anyone know exactly what needle comes stock in a 2000 WR.

How do you identify the needles in general, are they marked or something?

Carb comes out tonight for the BK mod.


Stock carb setup for a US 2000 WR400 is 165 main,OBDRS clip 3,42 PJ,

Also the jets are stamped, the needle has stamping near the top. If your eyes are not real good have one of your kids read them to you, thats how I do it.

Am waiting for a shipment of "E" needles, but am thinking of just raising the needle one clip.

Do you guys think that would hold me over till the "E"'s arrive?

Raising the clip will help but does not really approximate in any way changing to an E taper needle. It actually sounds like you might also be lean on the pilot circuit due to the backfiring, but it sounds like the lack of power may be partially remedied by the clip change. But the E taper will make your bike an entirely different animal.

I wouldn't be hammering on the E taper thing if it weren't so cheap and easy to do. It is definitely something you should try IMO. Keep in mind that whatever jetting you end up with on the D needle, especially main and clip (obviously) will not apply if you change to an E taper. Once you try the E you may need to change the main jet again, but you may find it well worth the trouble.

Hope this helps.

Well carb is out and the BK mod done.

My squirt was 2 sec. Not too bad. I make it .5 sec

Timing seemed a little late.

Backed out 2 turns on the timing screw and it still doesn't hit the slide.

I'm waiting for jets now.

If weather gets good I'll just raise the needle and see how it goes.

That YZ can really seems to lean the jetting from top to bottom. Surprisingly light too. A little loud though.

Can't wait to ride it when jetted.

Thanks for all the help

Backed out 2 turns on the timing screw and it still doesn't hit the slide.


I ended up zero to 1/4 turn in on all four (five??) bikes I've done this mod to. I'd be surprised if your bike doesn't hack and cough at 2 turns out, unless it was hopelessly maladjusted from the factory.

If you have replaced your throttle response with a big hacking wheeze the first thing you should do is go back in on the timing screw. I've always adjusted this more or less by feel and ignored where it was relative to the slide (unless I had some reason to suspect it was way off).

Hope this helps.

Sorry to be a pest. I was a little confused.

Turning the timing screw out makes the squirt earlier, no?

I was gonna turn it out till it hits the slide and then turn it back in a bit. Is this not a good idea?

Can it squirt too early?


Yes, in on that screw increases the delay.

I'm a bit of a maverick on this I guess, a lot of the BK mod posts you read the guys are setting this screw to have the spray just miss the slide. I prefer to leave it stock and see how it runs first, unless, like I said, I have reason to believe it is way off.

In my experience when you cut the accelerator pump spray by 2/3 or more you sometimes need to move what spray there is further ahead in the throttle range. The idea is that really you are seldom coming off idle, you are more likely to be somewhere above idle when you whack it open. If you have decreased the delay and are, for example, coming out of a corner at 1/4 throttle and twist it to 3/4 the pump may not operate at all, because with the reduction in delay the pump is "all in" by 1/4 throttle.

Ride it and see what happens, but don't be surprised if your pump is all done before things get rollin'.

Makes sense to me.

Actually my bike ran good until the cold and the yzf pipe.

Now it seems leaner accross the board.

In the Hot weather it would only stall if I blipped and then closed the throttle, like say setting it up for a berm.

Seems I was pumping gas in the motor and then shutting down, kind of loading it up with fuel it couldn't burn.

Bang! it would stall.

The "bog" was hit or miss. Usually happened at the worse time like timing a wheelie over a fallen log (ouch).

Other than that it ran great. Vortip or no vortip.

I think I'll leave it stock and check how many turns it can take before hitting the slide, that way I'll know how far I can go, if I need to.


Actually my bike ran good until the cold and the yzf pipe.

Now it seems leaner accross the board.

That just convinces me even more that you need an E taper needle, the only thing that puts any doubt in my mind is my lack of experience with the 400, although your bike does have the same carb as mine.

And not to totally beat a near-dead horse but I thought I'd point out that where your idle setting is also will affect where you end up with the delay screw.

Bottom line is that you should set it where it feels the best, that is the whole point. To that end I think starting from the stock position is a good idea, but if you are unhappy there I would guess that more delay, not less, will improve things. In my experience 1/4 turn is a big deal on this screw, so if you go 1/4 in one direction and things don't improve go the other way.

Hope this helps.

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