Stalling Trouble!

I have a 00 WR, with power core IV, & no air box lid. So far I have been able to leave it with the stock jetting. It has been running grate like this but lately I will be sitting at idle, drop it In gear then start to twist the throttle and it stalls, it has also been stalling in tight wood more than it used too. I have been reluctant to mess with the jetting because I don't know what I am doing. Is there anything simple that I can try? I live near Va. beach so I am near sea level; it's very humid in the summer. (If that maters to a carb?!:eek :)

Try turning the fuel screw out a quarter turn at a time, Before you do this turn the screw in and count how many out it is so you can go back to that setting if needed. This is the easiest thing to try. From there try moving the needle clip down one clip postion to the number four position.

You should also check the accelerator pivot arm. Is the pump rod centered in the hole? If not correct it by bending the tab out or in.

I would suspect that if the bike starts right up after it dies you just have a lean condition. I live in Wilson, NC and can relate to the weather and jetting. I 've finally got my bike very close with the help of Clark, Bryan and others on this site. What is the timing on your WR? Have you looked at the plug?

You may also email me at

or call me at 252-243-0337 work or 252-206-5786 home.

Good Luck



86TT225, 98CR80, 99WR, WR timing, throttle stop trimmed, air box lid removed, White Bros head pipe, silencer and air filter. Odometer and headlight removed. Moose hand and mud guards.

Messing with the carb is easier than rebuilding the motor after you have toasted a valve.

Running the motor for extended period with the jetting too lean can damage the motor.

Check with the jetting section of the web site and make the adjustments. It may save you from rebuilding the motor later on.

Thanks Bill, I will give that a try. In answer to your question the bike has WR timing, I don't think I will change that any time soon. I did put the 426 throttle stop in. I am thinking about going to the 13 tooth front sprocket. The trails I ride are super tight. How far is Wilson from Chesapeake Va.?

I was up your way during Thanksgiving, it's about 2 hours or less. You should come down and ride with us. We ride the woods or MX. The MX track is safe enough for beginners and fun for experts. We're doing a Hare Scramble in two weeks if you'd like to come down for that. I would guess from your set-up your lean. If you want plan a trip down and we'll jet your bike. I know what a nightmare it can be.

Tearing down the carb is easier than you would think. I've done it at the track to make jetting changes. Give me a call and I can tell you what I've learned.




According to my experience, normally when an engine was working OK and then invisibly commences to loose tuning up to the extent it is noticeable, first thing to wonder (given ceteris paribus condition) is to check simple routines like:

a) When was the last time I made changes to the bike that could affect the running of the engine? Are there anyone? If so, undo the mods you have made just to confirm hypothesis. Did you change permanently scenario since the bike worked fine? I mean altitude, humidity or other relevant parameters? Spark plug thermal value (hotter,colder)?

:) cleaning habits on the air filter and the procedure you apply to carry out is a very important point. To take the bike to limits of power requires extreme caution on maintenance items.

c)Learning the correct readings the spark plug color try to tell us is essential to interpretate engine illnesses. This is one of the best tests I know for the engine to reveal if it's running lean or rich. Re-jetting the bike is not always the best solution, especially if it was running all right short period ago.

d)Going from simple solutions to more complex ones is the most practical path you might find (easier to say than to practice !!!)

Sorry, I could hardly gather a couple of neurons for 5 long minutes and the time is up....

Regards from Chile


You cant even spoke proper England soon :)

I agree with all these comments (except Fluke, let's see if you can fluently speak 2 languages)). The carb, while complicated, is easy to work on. You are way too lean, don't ride the bike until you rejet. This is a race bike, not a gas up and ride bike.

My guess is changing the screw (counterclockwise is richer) position will help, but a 45 pilot is probably advised. It takes 20 minutes to change the first time, 10 minutes the next time.

Get used to working on this bike-with a minimal tool set, it's easy, really.

The one big thing to be aware of is make 1 and only 1 change at a time. Goto a 45 pilot, warm the bike up (2 miles riding) then adjust the pilot screw based on sound, throttle feel under load, and spark plug readings.

Once satisfied with the low throttle response, toss in a larger main jet-maybe a 168 or 170. Don't skip sizes too much, you'll be sorry.

Let us know if you need help with the actual procedure, it is a piece of cake!

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