Need some jetting examples for a WR '99

14 replies to this topic
  • Ynahg

Posted April 18, 2001 - 12:21 AM


I'm really getting crazy trying to jet my WR400 (mj 175, pj45, clip 3, 2,5 turns open) :)
I would like to have the input of guys who are riding the same bike (riding at sea level)
The bike is fouling plugs like crazy, and backfires when cold (carb slide !!!!!!!!!!!). Could it be the TPS ?

Thanks :D

'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

  • Taffy

Posted April 18, 2001 - 06:29 AM


a 168 MJ should be enough.

your pilot screw is way too far out.

try 1 1/2 turns tops,1 would be even better. it's not your tps, it's not your carb slide.

when did you last clean your air filter?

Taffy (99wr)

  • Ynahg

Posted April 19, 2001 - 03:29 AM


Thanks for your advice Taffy

I tried a 168 MJ yesterday evening and it seemed to work fine.
I'll test the bike this weekend and check the plug, and do some fine-tuning on the pilot screw.

Thanks a lot. :)


'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

  • freestyle111

Posted April 19, 2001 - 07:18 PM


im at see level i have wr400 and yz timing,with my stock exhaust and baffle out bike ran best 175mj,48pilot,dvpneedle 3rd clip,airscrew 2 turns out.i just put on whites bros.e-series promeg silencer[w\7 disc and bike ran a little lean.]so far best settings with silencer are 178mj,45pilot,dvp 3rd clip,air 2 1\4 out.when i bumped mainjet up to 180,pilot 48 and airscrew 2 out and it was little too going riding tommorrow so i can experiment a little bit more with my jetting and silencer discs combination.ive found you never know if bike is running at its best until you have jetted bike both lean and you have 2 points to work also helps with the understanding of how the different jets,sizes or settings will affect your motors performance.

  • James_Dean

Posted April 19, 2001 - 08:54 PM



Try clip #4 and turn the pilot screw (fuel not air) in a little.

  • Taffy

Posted April 19, 2001 - 10:14 PM



when you say you turned out the air screw 2 turns etc, you meant the one underneath the floatbowl. correct?


  • Ynahg

Posted April 19, 2001 - 10:16 PM


Tested the bike with the 168 mj (45 pj,4#,
2 1/2 turns out, it seems like i lost a little top end ??.
Going to try a 170, to check the difference.


'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

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  • James_Dean

Posted April 20, 2001 - 06:02 AM


With two discussions going on at one time things seem to be getting confused.

Ynahg, If you are using a stock DTM needle, clip #3 was a good idea to avoid plug fouling. Turning in the pilot screw was good advice from Taffy to reduce plug fouling also. My experience with a #45 pilot jet has been 1 1/2 to 2 1/4 turns with the baffle out or YZ exhaust.

The clip #4 suggestion was for freestyle111.

DVP#4 or #5


[This message has been edited by James Dean (edited 04-20-2001).]

  • freestyle111

Posted April 20, 2001 - 08:31 PM


it rain all day never got to ride.i think your right about needle at 4th clip that is one of changes is was hoping to try today.

  • freestyle111

Posted April 20, 2001 - 08:33 PM


yes,the airscrew underneath float bowl

  • Ynahg

Posted April 23, 2001 - 02:33 AM


My needle is a DXM needle ?? :)

Never heard about it here or m' i blind :D .


'99 WR400 F, YZ exhaust, throttle stop trimmed, WR timing, airbox cover removed

  • Taffy

Posted April 23, 2001 - 05:47 AM


that's the same needle as i had in mine.

it makes your bike run quite lean. it is pretty much the same as a DVP but it sits 1 clip lower. so if the DVP is on clip 4 for someone else you must go to clip 5 thus raising the needle 1 to equal it.


i posed a question which was unfairly misleading. the screw under the carb is simply called the PILOT SCREW. the pilot airscrew is the name of a jet in the front face of the carb behind the belmouth. at present it is a #75 or #100 but it can be pulled out & replaced by a screw called the PILOT AIR SCREW. this can also be screwed in or out to represent the air jet sizes it replaced.


  • Ynahg

Posted April 23, 2001 - 06:19 AM


So in fact i maybe would have to try 5 th pos instead of 4 th.


  • Taffy

Posted April 23, 2001 - 11:03 AM



my point is that you can now go & look at any archive jetting info & keep that fact in your head.

JD will tell you.

if you can imagine 6 identical DXM needles & you lift them from the 4th clip to the 5th that's a DVM, one more clip & it's a DTM. in the 7th clip it's a DRM. if there was an 8th clip it would be a DPM. so it's two letters to a clip change.

of course keihin keep the needles the same length by adding 1mm off metal on the bottom & taking 1mm off the top so to speak but do tell me you get the picture.


  • James_Dean

Posted April 23, 2001 - 11:05 AM



Yes, DXM clip #5 and adjust the pilot screw a little leaner. The pilot screw may have been turned out (rich) because the clip was set to run lean.

With YZ exhaust you may still want the #175 main jet for top end power. Your plug fouling looks like it was from the pilot screw or something else... float level?

(DXM#5 = DVM#4 = DTM#3)



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