Another Stupid Jetting Question...


The spark plug wrench part number is: "5BE-2814F-00-00". Many prefer using a 3/8" drive ratchet with a 3" extention, a flex joint and the 5/8" spark plug socket...but the Yamaha tool is nice and compact.

Colder, denser air does indeed require more fuel...Don't worry about all the confusion. Make sure your engine is well warmed up to a safe operating temperature for testing and to avoid sludge formation and cold seizure damage. You can try covering part of your rads and check by touching engine as there is no thermostat to control cooling and a cold running engine tends to run poorly and foul plugs.

Also, an "E" needle has a 1.0 degree taper as opposed to the "D"'s 0.75 degree taper. "E" will allow more fuel than "D" at full throttle and require a smaller main fuel jet. I am also switching to an "EKN"...just have to wait till spring now...

Hey guys, lots of info to digest here. I've been doing a little testing myself & the leaner settings suggested are a bit confusing to me. I brought my bake down to stock jetting and started there. It was so lean that I could barely keep it running. Thought maybe I was still too rich & didn't realize it. Went with a 42 pilot, 75 paj, 162main, and dropped the needle to the #2 position. Wouldn't run at all.

So I decided to try the other way, richer. Got back to a 48 pilot, 75paj, 170 main, 200 maj, stayed with the stock needle at #3, much better & it was just about where I was to start with. Still popped & hesitated little around 1/2 throttle. Changed the clip to #4 position, which reduced the popping & hesitating and moved it to about 3/4 throttle. So I left the needle there and put in 172 main. YES, finally got it. Got rid of the popping & hesitating all together. Starts first kick, hot or cold, no more popping, and it's pulling harder up top now too.

If the leaner thing is supposed to work, I don't get it. Maybe there's something I'm not doing right. The FS has got me a bit confused too. The manual doesn't list anything as the fuel screw. Are you guy refering to the pilot screw? Maybe the idle screw? Where's it at on the carb? Right now my pilot screw is about the same as stock, 1 1/2 turns or so. Could that be my missing link with the leaner settings?

For now I'm gonna try and stay with where I'm at. Maybe look into an EKN needle and play some more. But if I do, I think changing the main jet back to a 170 may be all that's needed there.

Just my observations.

Also, just as a side note. Seems to me that when my bike is lean it pops and hesitates during excelleration. If it's too rich, it'll pop and backfire on decelleration.

Your findings are similar to mine. Quite sure the pilot screw and fuel screw are the same thing. Located on the bottom of the carb bowl near the front. I ride the same bike, had just switched to ELN on clip 3 and winter showed up. Would like to hear your results with the E needle. I think you may end up 165 or less on the main with E taper. Good luck.

Thanks for the plug wrench P/N

Got my jets today.

Anyone got a technique for removing the needle w/o taking the carb off the bike?

Think I'll be riding in the snow tomorrow!



EJN 3rd needle is in. AP is less than 1 sec, 1 turn out on the timing screw to quicken the squirt. (could still go 1 more turn out but didn't). 165 main and 42 PJ (2 turns)remains the same as stock.

Bike is much more responsive on the lower midrange. The hole right off idle in GONE. Now its snap wheelie city. This is gonna be fun. Still a tiny bit of pop on decel, but much better. I guess the 45 PJ is the way to go.

Upper mid range and top is still a little flat. I will try a 168/170 tomorrow and see what happens.

Frankly, the bike really doen't warm up all the way especially at 40mph on the road. Taped off 1/2 my flatland rad guards but I can still hold my hand on the rad and valve cover after riding, so I presume the bike'll run better in the warmer temps and slower speeds off road.

Anyway making progress. I can not say if wether the improvement down low is the result of the BK mod or the EJN needle.

BTW, pulled the plug before the mods and appeared to show no indication of rich running. A year old and clean save for a redish tint on the insulator I figured was more fuel additives than anything else.

More to come....

RL, you can change the needle without taking the carb off. Remove tank, loosen carb enough to turn it to the left, approx. 1/2 inch is all it will go. Its tight but thats how I do it. Clearance for the two allen screws on top of carb. is close. I trimmed the end of an L allen to shorten it up and thats the trick. Once the top is off it goes quite well. Use tweezers to lift the needle out. Have fun.

RL, I was just reading some old posts by James Dean. At the time he was riding a 2000 WR400, 0-1000 feet, 40 degrees. He was using EKN-4 170 main, 48 pilot and 100 PAJ. Sounds like your bike, altitude and temp.. I know what I would do.

Yeah, James recommended a 168 main and a 45 pilot.

Rode it again today. Temp was about 45deg. Bike ran even better. Was having too much fun to swap in the 168 main.

Noticed the popping was gone too.

I can now power wheelie in 4th gear. Gotta love it.

Power still tapers off on top, but this may be a consequence of the WR timing.

BTW Tctrailrider, what did the grey wire do for you?


RL, When I did the gray wire I was in the middle of some other changes, hard to pin down to effect. Gray wire at high RPM retards the timing, like a govenor, so to disconnect is a good thing. If you unplug it you can reinstall if your not happy with the disconnect. A lot of the free mods are changing the WR back to a YZF. Yamaha started with the YZF and detuned it for the WR. The gray wire only matters when wide open or close to it.

PS let me know your jetting when you nail it. I ride the same bike, 500 feet but its winter in Michigan and I am down until April, its driving me nuts.


Your carb is OUT OF BALANCE with the 48/75 combination...It's gotta definately be running like crap....Go with the below settings and it will work perfectly.

168 Main

45 Pilot / 75 Pilot Air Jet

Spend the 12 bucks and get an OBEKN needle and set it on clip #3.

also order a 55 SJ from your dealer to replace the Stock 65 SJ.

FS 1 1/4 turns out...

You will then be ripping....Garrrrr-on-teeeeed. :D

I guess I need to get all my YZ and WR clients to start posting their (after) results here. :)

Bonzai :D

Yep, somethings wrong with my set-up. I got it running fine at home & down the street at my nearest trail. No problems at all. However, I went down in elevation to about 3500ft and it wouldn't run at all. Immediately fouled the plug. Dropped my needle to the #2 spot to lean it out & got it running well enough to ride for the day. But by the end of the day, & at about 40degrees, it was popping again at 1/2 to 3/4 throttle. Gotta change this. I'm gonna try your suggestions, get the needle & jetting set that way too.

My question is about elevation. Will these settings work at 5000+ ft. My house is at 4900 ft and my riding usually goes from there up. Sometimes up to as much as 8500ft. What are you suggestions toward adjustment for elevation?

Thanks for your help!!!

Oh Ya! Exactly what's an "SJ" and where's it at on the carb?

Thanks again!

The SJ is located to the left of the main Jet in the float bowl (Recessed)

The 48 pilot must be used with the 100 Paj, not the 75 Paj, Otherwise it becomes way to rich as you increase in altitude, thus the reason you fouled a plug. The 45/75 is a great combination from sea leavel up to around 8500 feet or so...(Atleast thats how far I tested it in the W.VA mountains last fall) I suspect it would be good to around 10K though based on JD's charts. If the 48 is doing a good job at your base altitude you might just try re-balancing the carb with the 100 Pilot Air Jet and see what happens. I have had 2 or 3 bikes that it worked just fine in. I'm planning another trip to Colorado in May of next year to see some friends in the Springs....Cant's wait to get up in them there hills again.

Bonzai :)

I gotta' tell ya. I'm happy with just the BK and the EJN needle. I suspect the bigger main may help on the top, but we'll see.

Still starts first kick and all.

My lower midrange "moaning" noise is gone, now there is power down there!

I'd get the BK mod done and order the needle.

You're a bit higher than me so maybe you could try an EKP needle I/O the EKN?

Maybe try a 45 pilot jet I/O the 100 PAJ?


Ok for now I've got the 168 main and 45 pilot in. The fuel/pilot screw started out at 1 1/4 turns. The needle and SJ are on order. I put these in and wondered if this sounds right to you. The bike starts alot harder, cold anyway. Have to use the choke and kick it 6 to 8 times before it'll fire up. I let it run with the choke out till the rpms raise a bit then push it back in. It'll idle for a little bit as it warms up, then the rpms will start to drop. Once the rpms start dropping, within 10 seconds the bike will die. I've adjusted the pilot screw out to about 2 1/2 turns, stopping every half turn or so, with the same results. Will the 55 starter jet help this? Will the new EKN needle do anything at idle? Figure the starter jet just helps it get started, once running it's not really used, right? The needle also doesn't really begin to effect anything until the throttle is being used, correct? Do you think I may be going the wrong way with the pilot jet? Will going back to the 48 pilot and adding the 100 PAJ help this?

I'm just getting lost and confused now.


you're lost and confused because the blind are leading the blind that's why!

you need to run the bike on choke longer before turning it off. so why can't we run them for 2-3 minutes on choke? coz the choke chucks in more fuel. so what's the answer? to get a choke that gives slightly less fuel. as the engine warms up the mixture should gradually come down to the mixture you know as "idle". so with a smaller SJ we can still get it to start AND hang on longer before 8-stroking THEN when we turn the choke off the bike has been running 3-4 minutes, your helmet and gloves are on and we can go for a ride!

so that's why you go from a 65 'starter jet' to a #55.

the needle straight is the vast majority of your idle mixture and it's the last letter that denotes this. most are on a M, N, P or a Q.

the reason your bike is hard to start is because the plug has nearly had enough (as have i).


time and time again it's been said but when the bikes are slightly rich they misfire. when they're very rich or CORRECT they don't. and i note that all the hard work on jetting Qs was a waste because at the end of the day it was a package setting and too many people can't be arsed to get it right.

no wonder you (pl) call it the "idle".

Taffy :)

Taffy, what a laugh! you crack me up...

listen to taffy and you will be rewarded with a faster, more efficient, crisper, cleaner running, smooth idleing and very easy to start bike! I seemed to get all of this by going to his 'leaner jets' and 'richer needle' settings. Bit of a jackpot really.


Taffy...You still crack me up after all this time.....Did I not say change the SJ from the stock 65 to a 55...Hmmmmmmmmmmmm, I do believe I also said to change out the piece of crap stock needle to an OBEKN.......

The bottom line is that no matter which jetting set is used...Taffy's or Mine or somone elses The entire set must be used. You can't use bits and pieces....It just won't work....Taffy and myself have spent hours and hours testing this stuff and debating it back and fourth. Both jetting setup's work well..... I race mine every week with absolutely zero problems, and Taffy did the same.

Again: Mine.... (W/NO AIR CUT VALVE)

Summer: MAY-NOV

48/100 = PJ-PAJ

170/200 = MJ/MAJ

OBEKN (3) = Needle

FS 1 1/4 to 1 1/2 , depending on altitude

65 SJ

Winter: NOV-APR

45/75 PJ-PAJ

168 /200 MJ-MAJ

OBEKN = Needle

FS 3/4 to 1 1/4, Depending on Altitude

55 SJ

IT works well, But you gotta do it all. As Taffy stated, One setting does in fact affect the others.

Bonzai :)

Guess I'll have to just wait for the needle & SJ to come in then. Of course that'll take another week or so & waiting for parts isn't one of my strong points.

In the real cold weather, I "blip" the throttle 2 times to pump a little raw gas in. Has been a first kick starter with the DRS and the EJN needle. I may try the 55SJ also as I start on choke for 30 sec and warm mine up by cracking the throttle to high idle and "blipping" the choke every 5 secs or so. Sort of like conducting a "three handed symphony". After a couple of minutes I'm good to go.

I did notice a little less choke bliping was necessary with the "E" needle, but then it was 30 deg outside.

Get the needle and see what happens. My experience has been good so far. If it don't work then you can change every jet in the carb like Taffy suggests. That's what I'm gonna do, but I aint gonna do it when it is 20deg out.


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