Help with 1998 WR400F Carb


12 replies to this topic
  • anoldsman

Posted November 08, 2011 - 08:22 AM

#1

Ever since I looped my WR400 backwards from a wheelie, I can't get it to idle. The best that I can get it to work is when I loosen the throttle housing on the bar to remove any potential stress on the cables. It will now run but barely idle without the choke and the throttle stop screw is turned all the way in to get the idle up. Also, as soon as I give it any throttle input the bike stalls. I see four options, 1-order JD jetting kit and go through the carb, 2-send my carb into ZipTy for a rebuild, 3-find a '05+ carb, or 4-order an Edelbrock carb. Each has their good and bad points. What do you guys suggest?

  • ur2silly

Posted November 08, 2011 - 04:07 PM

#2

How hard did it hit the ground?:busted:

Since you mentioned the throttle cable; any way it got pulled or stretched some way during the fall? Perhaps one of the cables are binding somehow making it impossible to adjust the idle.

Could also be on the carb or intake system was bent, broken, cracked, or otherwise damaged from the fall.

Go over the bike carefully, especially the carb, looking for any damage. Check everything from the airbox all the way to the intake boot between the carb and the engine for any cracks/leaks. You might also disconnet the thottle cables completely and see if that makes any difference.

Make sure the hot start lever/cable is not damaged and keeping it engaged.

If you don't find anything maybe the float is stuck since the bike was probably up side down.:busted:

  • anoldsman

Posted November 09, 2011 - 07:03 AM

#3

Hahahaha…it hit hard enough to completely mangle my exhaust :busted: (replaced with a factory setup from the classifieds). I do believe that the cables were messed up. After I loosened up the throttle housing it helped but not enough. I have the carb out and I will go over all of the places you mentioned. Thanks for the help. :busted:

  • anoldsman

Posted November 14, 2011 - 12:44 PM

#4

I found a '06 YZ450F carb and throttle assembly / cable on Ebay. I put it on yesterday and it started on the second or third kick. It runs better than ever now. Thanks for the help. If anyone has the same problems, just let me know and I'll let you know exactly how mine worked. :busted:

  • YZBrad

Posted November 15, 2011 - 10:50 PM

#5

I found a '06 YZ450F carb and throttle assembly / cable on Ebay. I put it on yesterday and it started on the second or third kick. It runs better than ever now. Thanks for the help. If anyone has the same problems, just let me know and I'll let you know exactly how mine worked. :busted:


That carb bolts right up? The throttle position sensor plug is the same? Ive been having a heck of a time getting my 1998 400 to run because of carb issues. I've thrown everything at it, and broke down and finally took it to a shop and they couldnt get it to run either. If a later model carb fits and the bike runs better with it, I'd consider the investment.

  • RasmusDK

Posted November 16, 2011 - 02:34 AM

#6

It solves alot of issues with a new carb! I put a 08 450 on my YZ400. The TPS is plug n' play, the inlet rubber needs 2 min of work with a razorblade, else its pnp too. See this http://www.thumperta...ad.php?t=984742

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  • anoldsman

Posted November 16, 2011 - 10:24 AM

#7

My '06 carb bolted right on. I had to pull on the airbox boot a little but nothing even remotely hard. No trimming on anything to bolt on. I'm sure that I have to jet it though to get it perfect. Also, if you want the later model Hot Start to work you will need the cables and lever for that. I just re hooked up my '98 Hot Start but I haven’t had to use it yet so who knows if it works. I highly recommend giving it a try.

  • YZBrad

Posted November 16, 2011 - 12:36 PM

#8

Great advice, thanks! I might be ordering one up tonight. This carb has been driving me nuts.

What years should I be looking for? 05+? And if I get the carb without the throttle assmebly and cables, will my stock 400 cable lengths work?

  • RasmusDK

Posted November 16, 2011 - 01:23 PM

#9

no the old cables will not work for 05+ atleast. The carb house is different, in the new one there is 1 M8 and 1 M6 thread. On the old both is M6..

  • YZBrad

Posted November 16, 2011 - 06:14 PM

#10

Oh ok good to know, thanks for the info. Will the 05+ cables work with the old throttle?

  • RasmusDK

Posted November 17, 2011 - 02:35 AM

#11

not sure, but i belive it fits. I brought a throttle house, carb with cables, and clutch perch with the hot start handle, the newer clutch perch is an upgrade on its own, my clutch is way smoother with the new one. I got it all for around 200$ + shipping..

  • YZBrad

Posted November 17, 2011 - 11:35 AM

#12

Sounds good, thanks again for the help. Theres an 08 carb with cables on ebay for $150 buy it now that I think I'll buy. I'm sure I can find a throttle pretty cheap if those cables dont work with my throttle.

  • RasmusDK

Posted November 17, 2011 - 03:25 PM

#13

Sounds like a good deal ;-) for that price you dont get many spares for the old one anyway, and the new one is so much better! Remember the hot start ;-)




 
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