My WR400 is running horrible! Please help

7 replies to this topic
  • zimm17

Posted July 18, 2003 - 11:43 AM


My WR400 ('00) has been sitting for about a year in the garage. I had all the fuel drained from the tank and fuel bowl. I replaced the oil, fuel, and coolant. Now it starts just fine with the choke on, but revs really high. When I start pushing the choke in, it slows down, then just quits. If I give it gas, it quits. I let it warm up with the choke out just enough to keep it running and got it up to running temp. I had to adjust the idle speed way up to keep it running. I rode it down the street and the idle is all messed up. It will idle way fast (like 1/4 throttle or something), then will slow down after a 30-60 seconds. A blip of the throttle will do the same thing, way fast for a while, then it slows down. Then when I was playing with the idle speed, it just quit and blew all the coolant into the catch tank.

I just replaced the plug (which looked normal) and tried to start it. Same thing, only runs with the choke on.

What's going on? Do I need to tear into the carb? The bike is all stock and is practically new (only ridden about 10 times).



  • HaremScarem

Posted July 18, 2003 - 01:12 PM


Try cleaning the carb and jets real good using compressed air.

  • Hick

Posted July 18, 2003 - 01:20 PM


Did you drain the fuel before you parked it, or just before you started it again? Because it sounds like you have a clogged pilot circuit.

Hope this helps.

  • captain_S

Posted July 18, 2003 - 02:11 PM


Maybe the head gasket has blown?

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  • MN_Kevin

Posted July 18, 2003 - 03:03 PM


Try cleaning the carb and jets real good using compressed air. sounds like you have a clogged pilot circuit.

Disassemble the ENTIRE carb for the most thorough cleaning this world has ever seen! :)
Be sure you clean the main AIR jet and pilot AIR jet. The air horn must be removed to access these. The air horn is the section that is on the airbox side of the carb body.

  • the426master

Posted July 18, 2003 - 04:45 PM


Try cleaning the carb and jets real good using compressed air.

don't use air because air can run parts in your carb clean it with carb or brake cleanner but don't clean any plastic or rubber they might melt

  • James_Dean

Posted July 18, 2003 - 05:18 PM


Clean the carb and be VERY careful to note where parts go and reassemble the same way.

Look for debris in the pilot jet and accelerator pump areas in particular.

  • MN_Kevin

Posted July 19, 2003 - 01:43 AM


don't use air because air can ruin parts in your carb

In this matter, carb cleaner WITH compressed air may be your only hope.

Before you use the air, be sure you remove the parts that can be damaged, i.e. gaskets, o-ring, float.

The jets can be blown out still installed in your carb. Aside from the two air jets, all your jets will be blown from the underside of the carb. You will want to remove your fuel screw and ALL of the hardware that goes along w/ it.

On my 99 (very different carb), upon removing the fuel screw you will/should find a wicked tiny washer, o-ring and spring. Losing any of these is as easy as crashing!

I always recommend dissembling a carb in a very clean, very confined area. Whatever you drop SHOULD be very near. Try using a large (24" x 24" x 3"), shallow box to disassemble your carb in.


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