JD Jetting - other carb changes required on a '99 WR400

1 reply to this topic
  • Brian_in_Long_Beach

Posted May 26, 2004 - 01:55 PM


I have a '99 WR400 that I've owned since new and I'm finally getting around to fine tuning the jetting on. The ACV/octopus was removed per Clark's instrucions when I got the bike and I've only fouled a plug one time - at Downieville in first gear at ~7000ft. That plug has been in the bike since Sept. '01 w/o any problems. I'm pretty happy with the bike as is - 48PJ, 172MJ - I think, and a DVP needle - don't remember the clip position, WR timing and a stock exhuast w/Thumper Racing Quiet Core (gotta pass 96dB). I've only felt the need for more power 1 time at Moonrocks while trying to keep up with a 520EXC and 501FE on a uphill two-track in perfect soil. The 400 was just out muscled. What it comes down to is I'm a lazy bastard and I have something that works pretty well and starts very easily.

What other carb mods besides the accel pump squirt duration are required with JDs jetting kit - PAS, MAJ, etc? For those running the R/C axle collar how are you keeping dirt out of the accel pump diaphragm?


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  • The_Missile

Posted May 26, 2004 - 10:14 PM


I used stock jetting and went from there. I put on CRD pipe which had me drop my main to 168.
I had a 43 pilot but cjanged to a 38 but its too lean, massive pops on decel. I'll be putting the 43 back in. All this with the red needle on clip position #3 (from top). I live at approx 2000 feet and its +-20C here now.

Keeping the diaphrgm clean....cant remember which one I am using but its one of the following: the rubber cover from a mountain bike shimano v-brake OR the rubber cover from the barrel adjuster of an XT/XTR shimano mountain bike rear derailleur. Not perfect, but best i've fouind so far.


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