1999 WR400 rejet for stock pipe with baffle

3 replies to this topic
  • jivenene

Posted February 22, 2010 - 01:53 AM


Sup yall,

I would like to do some stealth riding in hostile territory, so can anyone out there suggest baseline jetting for a 1999 wr400 with the stock pipe with baffle installed? I searched for an hour, but could not find the info, probably because everyone was going the opposite way with a high flow pipe and airbox. I am currently running a Q4, and it is way too loud. here is the current jetting, which is pretty spot on. oh yeah, 80F and sea level (gotta love hawaii):

Needle: JD Blue
clip: 3
MJ: 168
PJ: 45
Fuel Screw: 1.5 turns out

I know it will kill the power, thats ok. i am assuming the new jetting will have to be way leaner, due to the lower O2 flow rate, but what sizes? 155MJ? 40PJ? clip in pos 2?

Mahalos in advance!

Edited by jivenene, February 25, 2010 - 12:50 AM.

  • jivenene

Posted February 26, 2010 - 01:12 AM


well, i emailed JD Jetting, and will list their response here for completeness sake:


The jetting will not be excessively lean, but still richer than stock to work best with the quiet exhaust tip and uncorked air box.

Try setting up your 1999 WR400F with the following jetting-

#45 pilot jet

1 ½ turns out on the fuel screw

Red marked needle in the #5 from top clip position

#165 main jet

(The standard kit setting was a #170 main jet with open air box)

Use the fuel screw to fine-tune the idle mixture for good starting and idling. The fuel screw may need to be re-adjusted. Expect the motor to run a little hotter with the Red marked needle too.



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  • jayh300

Posted February 26, 2010 - 07:22 AM


i just did the same thing on my wr... put a stock pipe back on it as the aftermarket pipe was too loud for me... It seems to run fine with no change in jetting yet, but we have been in a winter weather pattern and have only rode it around the house... and you can actually stand to be around it, and carry on a conversation with it running....

as a side note... never been a big fan of jet kits, but this wr i bought had a jd kit in it when i bought it, and it is dead on... i have never touched the fuel screw... it has changed my mind on that...

  • jivenene

Posted March 02, 2010 - 09:34 PM


For more completeness, here are the jetting reccommendations for above 6000 feet from JD Jetting:

Running the 1999 WR400 (with stock airbox lid) above 6000ft, set the needle clip position 1 step leaner, to the #4 from top clip position, and lower the main jet to a #160 from the kit. Use the fuel screw to fine-tune the idle mixture.




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