The Mysterious Throttle Stop

my friend and i took our wr's in for routine service to our local yamaha dealer (he has a '00 and I have a '98). the '00 still has the throttle stop on it while mine has it completely removed. i questioned our dealer about installing the throttle stop which fits the yz426 (i read in a post that this is the correct length). he said that he removes the throttle stop completely from all the wr's that they sale (even his own).n he also said that it doesn't hurt them with the stop completely out. all i want is the definitive answer. should the throttle stop (assuming it is the yz426 stop) be in or out? if left out, what are the dangers? will appreciate any info.

Good question Richard.

Some say to remove it completely. Some say you must shave it down and put it back in.

All I know is that when I got my 1999 WR400 last year, I took it out completely. My bike ran OK but had an annoying slight hesitation in the mid range and didn't rev very high. I had heard everywhere how the WR revs to the moon so, needless to say, I was a bit disapointed at it's performance.

I called Baja Designs in California (I love those guys) and described my symptoms. They told me removing the stop completely can make the computer get confused when the throttle sensor goes PAST full throttle and cause unpredictible results. They told me to grind it down and replace it as I describe in my tech section (for a 1999) and try it again.

I did this and went for a ride. The bike had NO hesitation and REVVED TO THE MOON.

Problem solved.

However, I've run across many other riders that have the stop completely removed and their bikes seem to run fine.

So, I'm guessing, as with many other things on this bike (namely jetting), that how the bike reacts with the stop removed depends on the bike.

But, folks I know that buy the bike get my advice passed on from Baja Designs (I love those guys), remove the stop, grind it down, and replace it just in case.


P.S. Sorry about the multiple plugs. But, they have always answered my questions spot on and are always eager to help me. That's rare these days and it is greatly appreciated.

You also need to consider what happens as the needle is extracted out of the needle jet past full throttle. The taper on the needle keeps on tapering causing the bike to start to run even richer on the top. Could cause symptoms like Bryan reported. It will depend on the size of the Main Jet and needle combination.

I personally feel that the stop should be accuratly set to stop the throttle slide when it just fully clears the carburetor throat!! This is where it belongs it allows consistent position for jetting the main jet and totally eliminates the possibility of any TPS confusion--case closed.


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