Throttle Stop Length???

9 replies to this topic
  • Steve_WR400F_#61t

Posted October 31, 2002 - 03:35 PM


Anyone know what lenght the throttle stop should be on a 2000 WR400? I bought this bike used and never checked to see if it was cut down to the proper lenght. My bike won't hit the rev limiter in 5th gear and even feels pretty flat near the rev limiter in 4th too. I'm running stock gearing and don't really wanna change to lower gearing either. It's already low enough and spins the tire too much on loose, sandy hills as it is. The more I look at this thing the more I think my jetting is pretty close to right.

Anyone think I'm on the right track?

  • mmbasa

Posted October 31, 2002 - 04:09 PM


I believe that you need to cut it down to 27 or 28 mm. You can do a search and find it. there are also pics that will show you where it is and how to cut it.

  • Steve_WR400F_#61t

Posted October 31, 2002 - 06:09 PM


Ok, did a search and reviewed some of the posts. However, I still don't see a clear answer to the needed length of the throttle stop screw once it is cut. Is the 98 & 99's different than the 2000's? Are the 426's different than the 2000 400? I've seen everything from "cut it from 17mm to 9mm" to remove 23mm. How can a screw be trimmed 23mm if it's only 17mm long in the first place? Someone out here has got to have some actual numbers.

Anyone actually have any problems removing the stop? I've seen where people warn others of having it removed. Some have with no problems. But I haven't read anything about actually having a problem because the removed it.

  • tk421

Posted October 31, 2002 - 07:06 PM


I have also read where the slide cracks due to the throttle stop being removed.

Instead, I would take the carb completely off the bike, remove the throttle stop and cut/grind/beltsand the stop so that the slide just barely clears the throat of the carburetor when it hits the throttle stop. It’s a trial and error method, careful not to grind off too much. A drop of red loctite on the throttle stop threads is a good idea when finished.

If you don’t want to do all that, you could just order a YZ throttle stop, should be the right length and you might be able to change it without taking the carb off.

  • mmbasa

Posted October 31, 2002 - 08:40 PM


Check this link, should tell you everything you need to know.

Then go to the mods section and check throttle stop.

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  • cjh426

Posted November 01, 2002 - 12:56 PM


hey whats up for what its worth i just cut mine on a wr 426 01, and the bike had an 1/8 of a turn on the throttle. so i cut the stop down 7mm so its close to a 1/4 of a turn now and boy does it make a big difference. well thats all i know for now. good luck

  • levy1

Posted November 01, 2002 - 03:56 PM


In stock form the screw looks to me to be about ½ in length. I cut mine down to the threads and I had a stumble at full throttle. I then ordered a yz throttle stop. Problem solved.

  • Mr_Toyz

Posted November 01, 2002 - 05:41 PM


Ideally every "stop chop" should be done individually. i.e. cut alittle at a time until the slide just clears the edge of the venturi, no more no less.

Good Luck!

Mr Toyz

  • x2smoker

Posted November 02, 2002 - 04:30 AM


7mm shorter than stock is what Yamaha supplied the new bike "shoot Out" magazines in '02.

  • Steve_WR400F_#61t

Posted November 04, 2002 - 10:51 AM


FYI for everyone:

I've done a bit of research since starting this thread and here's what I've found out.

The stock WR throttle stop is about 34mm in lenght depending on year. Some actually came out at about 32mm some around 36. It should be cut down to 23 to 24mm in overall length. Cut it to 24mm then check to see if the throttle opens completely. If it doesn't, cut off a little at a time until it does. Make sure you don't too short. That can let the valve open too much and do a couple of nasty things to the carb. 1st it could get stuck in the wide open position and send you flying. 2nd, it could damage the butterfly/valve and crack it. If this happens it could actually break, get sent through the carb, and then into you cylinder. Not a good thing. When it's right, use some red lock-tite to ensure it doesn't come out.

Also, some shops and dealers actually have the stops removed. This in effect does the same thing as cutting the stop too short. Most of the time there aren't any problems with this method, but due to some tollerance issues when the carbs are fabricated, this "could" be a problem. Either way, it's best to just carefully cut the stop down and save yourself from the possiblitly of some serious headaches.


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