What is...??

Have a brand new 00 wr400. Just above the chain, about 2-3" above is the bottom of the air box, there appears to be a 1/2" line coming out. It only comes out 2" and is sealed on the end. It actually has two small dead bugs in it???? is this normal or should this line be open and should I put a new one on re-routed?? Your help is appreciated.

This is a semi one way drain for the air box. Pull it off perodically and clean it out.



86TT225, 99WR, WR timing, throttle stop trimmed, air box lid removed, White Bros head pipe, silencer and air filter. De-octopussed. Works frame guards and Thumper Rad Guards, Scotts steering damper. Odometer and headlight removed. Moose hand and mud guards. YZ stock tank, IMS seat and number plate. Renthal Jimmy Button "highs" and Renthal Soft half waffle grips. AMA, SETRA, Happy Ramblers MXC.

Thanks Bill, you're always quick to respond and I appreciate it. I have lots to learn about my bike, and this place is the best. If I wanted to do some mods on my bike, like adjusting the carb settings, needles etc.., how difficult is it? I'm quite mechanically inclined, but have no experience with dirt bikes or carbs. My bike seems to bog when I open the throttle fast, so I know I will need to adjust the settings. Having never done this before, I'm a bit apprehensive about what I should be "screwing" with and what not. I'll keep looking in the manual to see if I can decipher it. My problem is I need to learn to analyse the symptons, and KNOW what screws to adjust and what they do. ( I hate being a rookie )


Your not the only one in the dark when it comes to the FCR carb. Guys like Taffy have an advantage in knowing the carb from road bikes. Guys Like James Dean and Clark Mason have the technical knowledge and willingness to really want to understand the carb. All three of these guys will take the time to make changes, just to gain higher knowledge of the carb and to extract that last bit of HP in a given throttle range.

I'm still in the learning phase of this carb and others are much more qualified to give you input. Here is some of the input I've received. Go into the manual and read what throttle settings are controlled by what jets. Go to the White Bros web site and read their technincal information on jetting for the E-Series pipe.

Mark your throttle housing and grip to see what exact throttle position you are having problems with. Write down what your current jetting is. Make only one change at a time, write that down. Be aware of temperature and altitude, record this also. Search for jetting related posts. Do this often, because it will take a huge amount of time to read all of it.

I could go on and on about this as do the posts from all of the ThumperTalkers. Don't hesitate to ask specific questions, include all the bikes modifications, riding temps, altitude and symptoms.

Your problems seem to be to be in the idle to 1/4 throttle settings. Start with the fuel screw and turn it in to see what it is set at now. Then turn it back out to it's current position and add 1/4 turn. If you get up to 3 turns out and the problem still exists, go one step higher in the pilot jet. Of course this could also be related to the needle and/or clip position...gee ain't this fun :)

By the way the clear hose is not a "one way valve". It is an indicator of water or foreign matter in the airbox. Loosen the clamp and let whatever out. Then re-install the hose.

Good Luck


Take that airbox cap off and replace it with some longer tubing, run it down the shock area. The stock plug prevents your airbox from draining, and you have to keep checking the plug.

Hey Bill, maybe that's why you can't ride in the woods, you've got water in your airbox :)


These bikes are finicky when it comes to banging the throttle open real fast. Try to roll it on a little slower. Turn your fuel screw out a little. Raise the idle a little might help, too.

My 2000 only bogged when it was stock. It felt like it wasn't getting enough fuel. It might still bog on the first few minutes of riding when it's cold, but that's normal.

The pilot and main jet are accessible under the bottom cover plug. The top cover needs to come off to get the needle. It's very easy.

Loosen the carb, remove the coil + tank, turn it to the right to get the needle (top cover). T-handle allen wrenches work great.

Chances are your stock needle will run OK, but even better different needles might dial it in even further.

Good luck.

Thanks for the input guys. I'm going riding next Saturday, (so long as this 6" snow melts) up at my dad's farm. Gonna bring the tools and see if I can improve on it. I'll let you know. Thanks

Originally posted by Dave B:

It actually has two small dead bugs in it???? is this normal

Dont feel bad dave. I started a ant farm in mine. hump.gif


Darin from Missouri - 1999 WR 400F

Enduro Heaven

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