Clark...Oh Jett-i Master please use the force to help me

I have followed lots of guidance you have given to other people in the WR400 Empire, but I'm still trying to understand the Jett-i force. I have a 00'WR400 Yz timed, 175 main, 48 pilot, 2 1/2 turns on the screw, DVR needle (stock YZ) in the 4th position (Tried 3rd already), plug is a very light tan I live in southwest Ohio at about 500-700ft. The bike rips just off idle to almost all the way to the top (Think I need to go to a 178 main) but my problem is that she stumbles from idle to some where between 1/8 - 1/4 throttle. :) Do you think the needle is too lean or is it something else? Thanks for all the helpful info you have given. :D

:) Forgot to tell you I'm running 12 disks in my e-Series S-bend pipe Thanks!

First go to a 180 main jet. If this does not solve your problems then get a DVP needle and run it in the number #3 or #4 position.

At your altitude with 12 disks in a WB e-series you will be lean on top end.


Clark I'll give it a try. I'm going to the track tommorrow so I'll let you know. Thanks for the info.

Hey Jay I have the same problem 00 WR 400 YZ timed 180 main 48 pilot fuel screw 1.5 turns dsp factory series taper pipe exhaust I am running a dsq needle which I understand is just one size different than the dsp on the tapper and 2 clips richer so I have it on the 2nd clip which is equivalent to the 4th on dsp. my bike studers the same as yours Im going to play with the fuel screw but after that Ill wait to see what you find.

I am having the same problem w/ my '99. Running 180 main, 48 pilot, DVR 4th clip, e-series 9 discs, 300-500 ft. The bike RIPS from 1/4 throttle up (when reving), but it stumbles and somtimes dies from 1/8 to 1/4, or if you whip open the throttle from idle. I'm going to try the DVP needle re: Clarks recomendation. I removed the throttle position sensior from the card, not realizing you shouldn't. Has anyone had problems with this? Is it setable?



Hey Guys! Thanks to Clark I'm close on the jetting. :D (Thanks Clark) This is the scoop. 180 main, 48 pilot, screw is at 2.0 turns, dvr needle 4th position, 12 disks in the e-Series S-bend pipe, YZ timing, 500-700ft. It will stumble and stall if you whip the throttle open off idle. After it is above 1/8 throttle it this thing totally RIPS! :) It pulls hard and even worked OK out in the tight woods for the short time Iwas there. I think I do need that flywheel weight since she's prone to stalling now, but out on the track it is great. I do have a question for Clark. When I changed the main jet today I noticed that two of the main jets I have say 175RD and 180RD. The rest of the ones I have just have a little star on them with the number. If anyone knows what this is all about please drop me a line. I'll pull the plug tomorrow and let you know what the color is like. I'm still in pursuit of the off idle fix. Keep me posted if you find out anything.

The jets with the little star icon are offical Kehin jets the others are knock offs made by someone else. They all should work fine. Myself I always use the Kehin ones. However, not all dealers stock the Kehin jets.

I feel you will be happer with the DVP needle as it is ever so slighly richer off idle to quarter throttle.

my $0.02 worth


Thanks Clark. Your technical help has been great and I'm going to order a DVP needle today. Plug color was good and performance was excellent with the jetting recommendation you had suggested. If there is anything I can do for you let me know. Thanks Again :)

I have a '98 and changed to YZ-timing, 180 main, 48pilot, Air cut valve (Octopus) off andd 2turns out. I found tickover unsettled and a hesitation 1/8-1/4 throttle.

I have since moved the TPS fully clockwise (as recomened by Stroker), this cured the hesitation and the bike pulled much better and smoother lower down and tickover is tickerty-boo :)

Clark or WR owners,

I see the discussion on jetting. My question is would you see it differently if the original issue was WR timing? By that I mean, my 2000 bike is currently without the airbox lid and has the carb modification. Now if I were to switch to a Power Core IV-2 (its being delivered this Friday)would you recommend a 175 main jet? Any ideas would appreciated. Thanks

Encinitas, Ca

No the jetting on the WR's as delivered is too lean after you do the basic mods (remove throttle stop, remove air box lid and free up the exhaust). In WR form the bike will run better if you richen up the jetting. I do not have personal experience with the 00 WR but would say a 45/48 PJ raise the needle one clip and go to a 172 or 175 main as a starter after the basic mods above. Other 00 WR owners will have first hand advise. Also see the jetting section.

In YZ cam timing form the jetting will be different since the breathing characteristics of the bike vs RPM have been altered.


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