WR400F carb help in MI

4 replies to this topic
  • C-ya

Posted May 05, 2005 - 08:08 AM


Hey gang, I posted this in the jetting forum, but I figured I 'd post it here as well since there are a few of us here in MI.

I took the carb off my bike last night to find out why it's wetting/fouling the plug so fast. It is a bear to start unless the plug is clean (sand blasted) or new, then it runs good when cold (air temp), and then it won't start back up until a clean plug is put in. When it was 35 *F outside, it ran better than at 65 *F. At warmer temps, it snapped & popped on steady throttle and really popped on decel, and it was hard to keep it running. It died several times, but always started back up until I grabbed a drink and went back for another run. No dice.

I guess I should add that the bike was last ridden (by the PO) in the winter here in MI. I had to pull the screws out of the tires (they are still in in the pic on my site).

Here's what my carb (1999 5GS1 00 (US model)) has:

MJ: 180 (stock is 168)
Needle: OBVDR (YZ400, stock WR is OBDTM)
Clip: 6 of 7 from the top (stock is 3)
Pilot screw: 2 1/2 (stock is 1 1/4)
SJ: 60 (stock)
PJ: 48 (dunno what stock is - manual doesn't list (Clymer), but YZ is 45)


Air box lid removed, exhaust gutted and the "tube insert" installed. It has 3 or 4 tubes of different diameters and lengths. Throttle stop shortened. Haven't pulled the valve cover to check cams. Gray wire is still intact.

Any help is appreciated. Trying to get ready for an HS on May 15.

Edit: After sleeping on it (and reading several other posts), I think I figured out the problem. Lean the needle and the pilot screw at a minimum, and possibly smaller main. Haven't checked the MAJ or PAJ yet. Will do that today. Am I on the right track? It would seem so, but I've never dealt with a carb with this many jets.

  • Oasis_Flame

Posted May 05, 2005 - 12:20 PM


Dude you are way fat on everthing. Put the 168 main back in with a 45 pilot and the needle on #4 clip. When you say SJ, are you refering to the slow air jet? Slow air jet should be a 75. The other air jet should be a 200. I think you'll find a main of 165 will work the best. Adjust air fuel screw as needed. Hope that gets you going. :)

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  • C-ya

Posted May 05, 2005 - 12:24 PM


Thanks for the tips.

The SJ is the starter jet. Never heard of that in a bike before this one. The book says the PAJ (pilot air jet) 1 should be a should be a 75 and 2 should be a 100. Of course, the exploded diagram shows a MAJ and PAJ, not 2 PAJs. That's why I need to see what they are, so I can tell which is which.

I'll check tonight and see what's there. Thanks again!

  • 96warrior

Posted May 05, 2005 - 07:27 PM


168 main, 48 pilot. Stock needle in the 4'th clipp for me. Will see how the J.D. kit changes things. Will post my feedback too.

  • C-ya

Posted May 06, 2005 - 08:00 AM


96warrior, what is your exhaust setup? Please do post the results of JD's kit. Also, please let me know what size mains come in it.

Edit: Found out the MAJ is 200, and PAJ is 75.


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