Fast idle, and more

Hey, my name is Brandon, and I bought a 1998 WR400 last week. I have been riding a 1990 XT600 like a dirtbike for the past 3 years or so, so the WR is a major upgrade to say the least.

In the little under 2 weeks that I have owned the bike, I have got about 200 miles in, but this Saturday I ran into my first SNAFU.

I did a short 20 mile highway ride to get to the off-road area that I was planning on riding at. When I got there, my idle was high.

A couple of guys that were already out there (it was like a commercial or something; EVERYBODY out there was on a WR or a YZ!) and when they saw me with the tank and seat off, they came to assess the situation. Fast idle, and we could not get it to come down. After fiddling with the Idle adjsut screw a couple of times, it started to "clank". The first time the "clank" reared its' ugly head, the guy around me thought that maybe I still had the kick starter down. That is somewhat like what the "clank" sounded like. After we heard that, I shut the bike down immediately. After that, I trailered the bike back to the house.

After I got home, I called the local shop, and the guy told me to look behind the Hot Start button for a loose vaccuum line. Sure enough, it was loose. I put that line back on, and fired it back up. The "clank" went away within about 2-3 seconds of the engine being started, but the idle is still high. Sounds like the throttle is 1/4 the way open. And, the exhaust pipe gets RED HOT within about 20 seconds of the engine being started. Sounds like a very lean condition, but I am perplexed.

Any thoughts or suggestions will be greatly appreciated.



Any thoughts?

i think your throttle slide plate has broken and it's been injested by your engine. fear not! it has happened to others before and it doesn't do any damage.

the way top check is to pull the top off the carb and pull the slide out. on the engine side is a plate that is prone to cracking around the circular recess that is part of it.

check it out. and if it isn't remember which way up you put the plate!!!!!

remember the cutaway goes at the bottom!


Excellent job Taffy!

After pulling the carb off, I find that the slide plate has deteriorated, and the lower right-hand portion, outside of the cutout, has been injested by the engine.

Now, the big question is: What do I do about it? Do I slap another plate in, fire it up and go? Do I need to take the head off and assess the situation? Crack the case? Nada?

Great call Taffy! Thanks for the help.


ride it like you stole it! it will have broken up and gone out the exhaust.


you will have got a shock at the price of a new plate by now. all i can suggest is that you do a search for slide plate or anything like that. someone was making them at a fraction of the cost. sorry i can't be more helpful but the search button will do the job.


If your looking for the part number has a parts fiche. Their in Ohio. My last little on line order of a few carb parts from them took nearly a month. (they delayed my order because two parts were on back order) On their web site they don't tell you this. The local Dealer won't have practically any normal wear and tear parts in stock so look for a good source.

By the way if you tried to hook up with me on my cell phone I couldn't hear it ring not 5 feet away from me in the garage While working on the WR. The PUD was digging up the street in front of the house for a water leak.

Tried to call back the number but either got ring ring, busy signal, or the blast of a computer or fax machine

Taffy, you are on it! Before I looked up the price of the plate, I am thinking "25-35 bucks, tops!"

Ha! What was I thinking? I have ordered the plate, as well as the seal that goes between the plate and the slide. Hopefully that will be on by the weekend.

Hey Mike! Yeah, tried calling you the other day, when you and Tim were headed out riding. We will have to get together for some riding, and I can pick your guys' brains for other things I need to be "heads up" about.

A functional speedometer/odometer is one.

Thanks for the help!


If Yamaha doesn't have the plate to you quick, Sudco has it on the shelf - for $85. Recheck this , but I think the part# was 021-030. (1-800-998-3529)

Good response Taffy!

Brandon, reference your wanting a speedo, I use a Cateye "Enduro 2" bicycle computer. It has worked excellent for the almost 2 years that I've had it. They're about $35, and Arlberg should have one. It shows speed, two separate trip odometers, cumulative odometer, etc. Another type, which many guys here on the forum are using, is a "Panoram" bike computer. Do a search on that name and you'll find plenty. If you get one, let me know. I have a bombproof method of routing and mounting the sensor wire and sensor. It's good to see you on a WR!!! :)

Right on Tim!

I went down a bought a Cat-Eye Velo 2 the other day, to put that on the WR, but the wire from the sensor up to the unit was just no long enough. So, you are saying that the Enduro one will work? Good enough for me. I'll pick one of those up. Got to get together with you, Mike, and Al for a ride. I think his soon-to-be father in-law is coming to town this weekend, and he is looking for a good desert ride. I imagine that we will be out at Crescent Bar both on Sat. and Sun.

Glad to be on a WR! Don't miss my old blue PIG very much, especially off-road.

Talk to you soon.


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