Don't do what I did ...


Don't do what I did!

I busted off the carb vent right next to the float boal drain/main jet access.

Usually I use a 14mm socket to get the drain bolt off. But, Saturday I couldn't find my 14mm so I used a closed end box wrench. This wrench is a little too thick and it put too much stress on the vent and it broke that little sucker right off.

I called two local dealerships and they told me I can't order just the float boal bottom of the carb. I have to order an entire carb ($850.00 US).

After quite a bit of swearing and yelling, I went to the hardware store and bought some JB weld and successfully welded it back together.


$850 for the carb. WOW. That almost knocked me off of my chair. Kehins for my old CR125 cost ~ $180.



2000 WR

Are you sure you can not get the bowl from a Mikuni Distributor? Sudco International is one and the other "biggy" escapes me at the moment. Thank god for JB weld though huh?


try carb parts warehouse. i think they are in ohio somewhere. try for website.

You may not be able to order if from Yamaha but I'll bet the carb manufacturer can sell you a new one.

Yeah, I figured I could get the part from somewhere else if it came to that. But, luckily, the good ole JB weld worked fine.

For that much money ($850) I could bag the stock carb and get that new fuel injected carb I heard about.


For that much money ($850) I could bag the stock carb and get that new fuel injected carb I heard about.

And what fuel injected carb would that be?


The Carb Parts Warehouse Catalog shows 3 possible float bowls for the FCR carbs. They may be able to help.

Earlier you asked about getting a jetting seminar and sometimes I think I could give one. Twenty years of charting and accumulating needles should make me qualified. I tried to write a lengthy letter to you with email but the server lost it.

I have written articles and sent them to Dirt Rider, Dirt Bike, and Eric Gorr. They just get to be too technical for most readers. Too bad.....

IMPORTANT NOTE: The jet needle chart for decoding WR/YZ400 needles is on-line. Go to the Carb Parts Warehouse----Site Map----Keihin Carbs-----Keihin Jet Needles----FCR(35-41)

James Dean

I'm bummed I didn't get your jetting info via e-mail. I wonder if the server was down that day? Please send again?

Here is the needle info James spoke of on the web site:



The text didn't get saved, I should have filed it first. I'm a novice at my home computer.

This is the all important chart though. Notice where the "D" taper falls, at the top. Has anyone tried jumping up to an "E" taper? With all the modifications going on and increased main jet sizes it seems worth looking in to. The chart shows 1.00 degrees is the "Standard" for the FCR. WARNING-This is uncharted territory. Start rich and work towards lean. The L1 (clip height) is critical to pick an acceptable needle. L1 is measured to mid taper (2.515mm diameter). A good starting point might be EMM#6 or EMP#5 for higher altitudes. These may be available from CPW as N427-OC-EMN (017-262) or N427-OC-EMP (017-264). The Yamaha manual lists their example needle as "OBDTM", and I do not know the difference between OB--- AND OC--- needles. Might work or might not....

The E taper needles listed as options in the YZ400 manual look like the clip height(L1) is far too lean to work(EVQ and EVP).

Just food for thought----

James Dean

Holy crap, Clark isn't going to like that chart. He spent who knows how much time measuring all those needles to figure out the code and all along the info was right here on this chart!


'99 WR400

'92 GSXR 7/11

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To the contrary Clark thinks the chart is way cool. :) However, Clark has benefitted from testing and has a stong feel for jetting this carb on the 98-99 WR's. Armed with this more conclusive info you must be vary carful and have a good understanding of the jetting basics before you consider each change. The table after carful study is very insightful and matches the measurments I'v taken. Remember Yam jetted this bike as delivered and for different world wide conditions. Nobody lives in a World wide condition you ride and jet your bike base on its state of tune/modification and the local conditions (Altitude, temperature, air ox content or lack there of, etc.). There is no one formula but based on my work you should be close and with a few minor tweeks dial it right in. The table provided is one more tool to use in solving the jetting equation for your conditions.

Good Luck to all


Well put Clark! Minor jetting adjustments are all that is needed for most riders. Nobody can know what suits your riding style, conditions you ride in, and the bikes state of tune better than yourself. Keeping a ride log with settings written down are very helpful.

Major jetting changes are not for the impatient and require lots of time and testing. Indescriminant swapping of needles is like riding in the dark, who knows what you will hit! I have opened up a Pandora's box with this needle chart. You may wish for more power and better throttle response, but it will come at a price. Move carefully and you will be rewarded.

Good Luck

James Dean


Where is your written report on the chart. What exactly is L1 how do you know this? Is the difference between OC and OB the taper at the bottom of the needle OC=straight section OB=continuous taper??? Any further insignt. It is obvious that going to the one degree taper "E" for the 426 alows the stock main jet in the 426 to be smaller than in the 400 with the "D" taper. Any comments?

Maybe e-mail me and we could continue this discussion off line and not bore the rest of the readers.


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