99 WR 400 jetting (again)

Sorry to bother everyone with this old saw BUT...I have a problem and no matter how many post's I read I cannot solve it!

My 99 WR which is stock apart from an E series with 12 disc's in and a quiet core due to noise issue's (young kids ) has a Massive hesitation from a steady throttle i.e. when you snap it open for a ditch etc it bogs, dies then pick's up like a good un! If you roll the throttle then no problem. The exhaust seems to get VERY HOT very quickly.

I have checked the APJ timing and duration and I am just missing the slide and a duration of approx 0.75 sec's give or take.

The main jet is a 172 and the needle is stock as an OBDTM on clip 4 NO idea though about pilot etc.

I need some ideas where to start cos I dont know nothin...but I 'm willing to learn from those who do

many thanks

Carb; 150MJ, 160MAJ,EMM-clip 4, 38PJ, 55PA(J)Screw, PS 1.5 and no APJ!!!


This is what the Taffster settled on. Missle from Switzerland is using these settings and is impressed. There is a slight lean spot, but he working with it. I know this is a GIANT leap of faith, considering everything has changed.

I do not know if Taff is de-octopused, or how that will effect jetting.

I do know our semi retired other Carb Guru, James Dean, is intrigued with these settings.

I am using an EMN needle right now. My main air jet SEEMS to large (#220) even w/ my 170 main jet.

Hopefully one of those guys can help you out here!

Guy: You and I are running the basically the same setup. I am doing some fine tuning on my jetting tomorrow. What I have now works with the air box cover ON. But I want to remove it. Keep an eye on my other post "More changes to Come" that is where I will be posting my change data. You can e-mail me off line and I can assist you with other mods you can do to your 99 that will make it a fire breathing dragon.

Bonzai :)

:) OK people thanks for that....if I leave it in a higher gear ie 3rd at walking pace then snap the throttle it just bogs and wont pick up at all now is this a sign of rich or weak ? should I raise or lower the needle?

I feel a headache coming on...perhaps I'll take up Knitting!


OK....... Anyone with any helpful hints on knitting for Guy. :) Sorry Guy I could not resist, you are in good hands here -- be strong and put the knitting needles down. Also, make sure you are using the correct jetting needle, not a knitting needle in your Carb. :D


:) Thanks for that Pete...Phew that was close... I nearly dropped a stitch there LOL :D

Right next instalment..... I have taken the needle to clip 2 and there is an improvement... also remove the airbox lid..again an improvement so I conclude that the bike is jetted too rich stock for a UK bike (99) is 168 and I'm on a 172 (came with the bike !) so I have ordered a 170 and a 168 should be here early next week so I will try that......Also I hace checked the needle again and it is a OBTDXM not a DTM.

IF anyone thinks I'm doing wrong then please please post and tell me...I am a Numpty where jetting is concerned, this is my first foray into the Dark world of jets, tubes, rich weak etc etc!



[ December 01, 2001: Message edited by: Guy ]

Right I spent this afternoon with the carb in bits and the settings are as follows :-








pilot screw 2 turns out

This is how I got the bike and not what I have done to it!

Does this sound about right for a UK bike?

I know the MJ is out it should be a 168 as stock and the clip should be 4 but I can find no settings for the other jets in my manual



The DXM should be in something more like clip #5 and maybe #6 with the pump spraying only .75 seconds. This is the most lean needle from Yamaha along the tapered section. Are you counting from the top? The other settings are close to stock and look good.

Hi James,

Yes I am counting the grooves from the top, when my jets arrive on Tues, I will be trying them out and I will post back then....

Would the pilot screw being so far out (2 v's 1 1/4 turns) have any major effect??

:) YES!!!!! success....having returned the MJ to the stock 168 and the PS to 1 1/4 it is like a different bike...

2nd run.... raised the needle to #5 even better! :D now it wheelies off the throttle in 3rd...

5th still a little breathless, so I am assuming it is a little lean, so as per JD's post I will try #6 on the needle, I have also removed the airbox lid, so I think it will need to move a clip..

but what a difference it has made :D:D

I began to think I'd bought a lemon, but not so!

Many thanks to all of you who took the time to reply it is much appreciated

One happy boy! :D:D


Good work !!!!! Now dont let all that power go to your head :) Ride safe and have fun.

Pete :D

:) Thanks Pete :D Raised the needle to clip #6 tonight, even better still!

I think when the W/K'nd gets here I may even try #7 :D

I have perfected the art of carb removal in about 5 mins thanks to JD and Taffy, I havn't moved the top engine mount, doesn't seem ness, just undo the cables at the throttle and Bob's yer Mother's Brother!!!(that may catch a few of you out HE HE! :D )



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