Carb cleaning on 99 WR400

Anyone out there had to rip into your carb to clean jets? If so are there any good tips that I need to be aware of? I hear that you don't want to mess with the throttle position sensor. Also, I'm at about 5500 feet from sea level. What jets should I be running? (main, pilot, starting pilot)



One more thing on the jetting. I will be running it from about 3500 to about 6500 feet? Will one jetting setting be adequate for all?

First off,

The throttle position sensor, very often, is out of spec. The manual covers setting it correctly. Do not ignore your TPS!

The accelerator pump diaphragm is VERY PRONE to dirt AND WATER intrusion. When disassembling the AP, WATCH FOR O-RINGS. One in particular seems to be overlooked by lots of people, and dropped. Cleaning this OFTEN is recommended. DON'T BE SURPRISED to find your AP seized and/or rusty!!

THE AP on the 98/99's were SEVERELY whacked on setup. It would behoove you look into the Taffy Mod on accelerator pump adjustment. This AP has really zero adjustability from the factory. Taffy's mod will mimic the infamous BK mod.

MANY of us have drastically altered the jetting. [Moderator] Bill from PA has some numbers that SHOULD work for you...


The first time, I would take off the carb, clean the outside thoroughly (aerosol parts cleaner), and put it into a large flat pan (like a big baking pan or your oil drain pan) both to keep it clean and so I wouldn't lose parts. I would make at least mental note of all vent tube routing. Then I would take off the airboot joint (short pipe on inlet side) and the intake joint (short pipe on the outlet side). The airboot joint will uncover the main air jet and pilot air jet. Then I would take off the bowl. This will basically uncover the float. Take the float hinge and float off and you will uncover the starter, pilot, and main jets as well as the needle valve. On the bottom of the bowl is the accelerator pump (3ea 3mm allens). Take the jets and needle valve out, blow carb cleaner into all the orifices, let sit, and then air. Clean all jets with carb cleaner, let sit, and blow with air. All jets should have round holes through the middle. If they're not round, something is in there. In addition, the pilot has cross drilled holes in sets. You should be able to see through them. Finally, use parts or carb cleaner and clean out the AP assembly.

Taking the top off or the throttle slide out, doesn't help clean any jets or passages.

Good luck,


Taking the top off or the throttle slide out, doesn't help clean any jets or passages.

True. But it is a good opportunity to see how the needle comes out. There isn't a need to take the slide out though.

[ May 26, 2002: Message edited by: skthom2320 ]


The settings in my signature are for sea level to 2,000'. You might have to go leaner on the MJ and PJ.

If the carb has not been de-octopussed, you may want to. Look in the technical section for information on "how to".


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