New (to me) wr400f

6 replies to this topic
  • MicahRoss

Posted July 13, 2008 - 03:30 PM


I picked up a 99 or 2000 wr400f the other day from a guy at work. He forgot the exact year but thinks it's one of those years and Oklahoma didn't title dirt bikes back then. He gave me two sets of front forks and all the riding gear I needed. I got it for 1500 bucks, hope I didn't get ripped off. It runs good and has more power than I need, but I do have a question about the idle. It seems to idle high all the time. Is there something to look for other than a vacuum leak. It does have an after market pipe on it and I don't know he re jetted it or not.

Sorry but I am new to dirt bikes so any help would be great.

  • Alternative

Posted July 13, 2008 - 05:58 PM


First, have you tried adjusting the idle speed screw? If it used to idle properly then I would pull the carb apart and have a close look at the slide plate, on the <2001 models with the 1st gen FCR they are known for cracking and breaking and being ingested into the engine. Unfortunately the only real cure for this is to buy a later model FCR carb, if you just replace the plate it could break again. If the plate looks fine then clean all the jets and fuelways in the carb and try it again. You may need a bigger pilot jet if the guy didn't rejet for the new exhaust.

  • MicahRoss

Posted July 13, 2008 - 06:48 PM


Ok I will pull the carb tomorrow after I get off work. Thanks, Micah

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  • matt4x4

Posted July 14, 2008 - 07:29 AM


The WR 400 was made from 98 to 2000, you should be able to get the manufacturing date off the label on the front of the frame near your triple clamps.
Before you pull the carb, turn the idle screw out a little bit (while warmed up and running, get it down to about 1300rpm - usually just above setting it to smooth not choppy - this should be your starting point.
Now, if you have an aftermarket fuel screw (a knob under the bowl - front of carb - goes up inside) you can play with this screw, if you don't, you need to get a small short flathead screwdriver and place it up in the hole in that same location to adjust the factory fuel screw.

Before adjusting it (with bike off) turn this screw in until LIGHTLY seated - counting full turns - write this number down.
The fuel screw adjusts the pilot jet fuel output ever so slightly and only works in the 1.5 to 2.5 turns out from seated positions.

So, having counted revolutions to lightly seated, bring it back to where it was.
Start bike - warm up for 10 minutes.
Now turn fuel screw in until idle drops, from here, turn it out (there will be an area of about 1 revolution where noting really changes) counting turns again until idle changes.
Back the screw in half the number of turns of what it just came out and that will be your proper setting.
Turn your idle screw out to bring it down to a nice smooth idle but not racing.

(You can count revolutions of the fuel screw until lightly seated again (write it down) just to see if it falls within 1.5 to 2.5 turns and if it has changed from your earlier setting.)

Now, if your bike bogs on acceleration, it may be a part of the carb that's dirty, or broken, but we'll get to that then (if needed).

Whatever you do - do not remove the black TPS off the carb when cleaning, just unplug the wire.
Your bike should have good 0-1/4 throttle response at this setting, if not, you may have to go to a different pilot but it will likely be ok.

  • Alternative

Posted July 14, 2008 - 06:00 PM


Nice write up Matt, very well explained. The reason I told him to pull the carb first was if it is a cracked or broken slide (as the early FCRs were notorious for) then he'd risk damaging his engine continuing to run it like that. I've seen what broken slides can do to valves, not pretty :thumbsup:.

  • MicahRoss

Posted July 14, 2008 - 06:19 PM


I pulled the plastic cover off the throttle side of the carb and found that the return cable is fraid so I will start there first. Where would I go to find the year per the VIN? Thanks, Micah.

  • matt4x4

Posted July 15, 2008 - 04:27 AM


It's a bit harder to get the year from the vin - try emailing Yamaha and they should have records - mine has month/date on the sticker...

Alternative - you're right. Probably a good idea to check the slide.


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