2000, wr 400 Carb woes off idle bog HELP


5 replies to this topic
  • augino

Posted February 13, 2008 - 11:33 AM

#1

:applause: Hey i need a little advice on my 2000 wr 400. i have had the bike since it was new. it ran fantastic for better than five years before it started to have trouble with the dreaded off idle bog. whenever i flick the throttle it wants to cough or die. even when riding.

i have printed and read several articles and tried everthing i could form the good info provide in the tech forums.

i have taken the carb off at least 15 times to try different settings in the carb. i have replaced the Ap diaphram, the air cut diaphram, changed the jetting up, down sidways and back agin including the pilot jet. the needle clip up down and back again, this also includes changing the fuel screw in 1/4 turn incriments through every change i made. i even installed a new (red) needle form the JD kit i bought for my 04 450 to see if anything would change. and it didn't change a thing. i ahve repalced the stock fuel screww with and aftermarket one that i can easily adjust on the trail. i also replaced the "O" ring

the funny thing is that the bike always starts with one or two kicks at the most. through every setting change the bike has run strong , maybe a little backfire now and again but the bog just wont go away. the power rolls on strong and with pleanty of power. it will lift the front end in 1st through 3rd.

but flick that throttle and out she goes.

i have read several articles including the one that the guy showed how to install a leak jet in a non- leak jet bowl but this carb worked great for years. if it needed a leak jet it would have never run right. somthing has changed.


I have checked my TPS reading with a closed and full throttle and they are all within spec.

my AP shoots a nice 6ft long stream of fuel. i have placed a dowel under the slide and adjusted all of the freeplay out of the AP lever. whenever i made a change to the jetting i reinstalled the carb, started it, checked different settings on the fuel screw and well as the AP adjutment.


does anyone have any suggestions?? please let me know if you have any ideas?? its a FCR MX 39 carb on a wr 400

  • dirtysouth

Posted February 13, 2008 - 12:05 PM

#2

:) Hey i need a little advice on my 2000 wr 400. i have had the bike since it was new. it ran fantastic for better than five years before it started to have trouble with the dreaded off idle bog. whenever i flick the throttle it wants to cough or die. even when riding.

i have printed and read several articles and tried everthing i could form the good info provide in the tech forums.

i have taken the carb off at least 15 times to try different settings in the carb. i have replaced the Ap diaphram, the air cut diaphram, changed the jetting up, down sidways and back agin including the pilot jet. the needle clip up down and back again, this also includes changing the fuel screw in 1/4 turn incriments through every change i made. i even installed a new (red) needle form the JD kit i bought for my 04 450 to see if anything would change. and it didn't change a thing. i ahve repalced the stock fuel screww with and aftermarket one that i can easily adjust on the trail. i also replaced the "O" ring

the funny thing is that the bike always starts with one or two kicks at the most. through every setting change the bike has run strong , maybe a little backfire now and again but the bog just wont go away. the power rolls on strong and with pleanty of power. it will lift the front end in 1st through 3rd.

but flick that throttle and out she goes.

i have read several articles including the one that the guy showed how to install a leak jet in a non- leak jet bowl but this carb worked great for years. if it needed a leak jet it would have never run right. somthing has changed.


I have checked my TPS reading with a closed and full throttle and they are all within spec.

my AP shoots a nice 6ft long stream of fuel. i have placed a dowel under the slide and adjusted all of the freeplay out of the AP lever. whenever i made a change to the jetting i reinstalled the carb, started it, checked different settings on the fuel screw and well as the AP adjutment.


does anyone have any suggestions?? please let me know if you have any ideas?? its a FCR MX 39 carb on a wr 400


No expert here but try a new plug...quik and easy. Good luck with this issue. I know that probably isn't the most educated answer but I usually try all of the easy stuff that I may look over before I go diggin deep.:applause:

  • William1

Posted February 13, 2008 - 01:58 PM

#3

Being your bike ran great for five years and is now five years old, I would disassemble and inspect all the AP parts. Make sure the plunger rod is free of rust/corrosion. Ensure there is no debris in the AP chamber, that the diaphragm is in good condition and all parts appear to work smoothly..

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  • ncampion

Posted February 13, 2008 - 07:46 PM

#4

Next try an Edelbrock carb. That fixed the problem on my 400 and two other friends. FCRs suck. Remindes me of 80's auto carbs when they tried to make them run with the smog rules. Then came EFI and the world was right again.

  • augino

Posted February 14, 2008 - 03:20 PM

#5

everything on this FCR carb is clean as can be. i have a new AP diaphram i have cleaned it with carb cleaner and compressed air at least 10 to 15 times. i get a 6ft stream of fuel squiting inot the motor. its just baffleing! i think i may try another JD jetting kit and see how that works

  • Ruff 400f

Posted September 29, 2009 - 05:08 AM

#6

I have a 2000' wr 400 as well. Have you heard of the splitstream or quick shot thingo you stick in the inlet side of you carb boot. They reckon it helps, i'm thinking of trying it out.




 
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