200 main air? is that for real?

5 replies to this topic
  • matt_patton

Posted May 12, 2005 - 04:20 PM


I got a 3rd hand '00 WR400 and put a pod air filter on it in addition to the FMF Q that was on it when I bought. But it runs a little wierd so I figured I'd rip the carbs apart and see what I have. PO claimed it was jetted. Well, I guess. I pulled all hte jets and this is what I have.

168 main
45 pilot
168 starter
stock needle #3 slot
200 main air
75 pilot air
1.75 turns on idle mixture screw

Now that doesn't look so bad except for the 200 main air. Has anyone seen that before? BTW is the idle mixture screw what some people call the "fuel screw"? I'm guessing it is as nothing else makes sense.

I'll repost about drivability again when I test this filter vs a stocking to see if this filter is really breathing enough. I don't think it is.

  • Seabass

Posted May 12, 2005 - 04:43 PM


The MAJ on my '05 Wr 450 is a 200. I'd imagine yours would be the same.

  • C-ya

Posted May 12, 2005 - 05:22 PM


Main Jet: 180 (stock is 168)
Needle: OBVDR (YZ400, stock WR is OBDTM)
Clip: 5 of 7 from the top (stock is 3)
Pilot screw: 1 1/4 (stock)
Starter Jet: 60 (stock)
Pilot Jet: 48 (dunno what stock is - manual doesn't list (Clymer), but YZ is 45)
Main Air Jet: 200 (stock)
Pilot Air Jet: 75 (stock)

Listed above are my settings for a '99 WR400, with stock noted where known.

It doesn't sound like it is "jetted" for the pipe, which may explain why it runs weird. Of course, that 168 SJ may also not be helping.

And yes, the fuel screw is often referred to as the mixture screw.

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  • slotracer577

Posted May 12, 2005 - 05:23 PM


A 200 main air jet is in line with what I have seen on other FCR carbs in 4-stoke applications. I think it is the biggest one they make. The function of the main air jet is to keep the bike from going rich on top end. Smaller makes it go richer.


  • matt_patton

Posted May 15, 2005 - 12:09 AM


I'm having way more trouble getting jets than I figured on. Local tuner shops have very little in Keihin - all Mikuni. Can anyone tell me if we have style 22 or 23 pilot jets, and if we have 13 series Mains? There's this notion of KJ and CR prefix main jets. All mine have is a 'k' or a star on them.

  • C-ya

Posted May 17, 2005 - 05:30 AM


If you want Keihin, order stock ones from Yammi, here, or http://www.powersportspro.com. It would seem that since a Keihin came stock (OEM) that the OEM replacement part would be a Keihin. Just guessing, but I'm thinking Yamaha doesn't do jets.


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