2000 WR400 with YZ400 head won't start


6 replies to this topic
  • NBinSD

Posted September 13, 2008 - 02:14 PM

#1

I toasted the head in my 2000 WR400. Got a '99 YZ400 head and put a new piston in and put it all together. When I kick it it sounds like it wants to start but it never does. It's got spark, fuel, and compression. Is there something different about the YZ head that I need to change? Timing the same? Any other ideas?
thanks,

-NBinSD

  • husky300racer

Posted September 13, 2008 - 02:16 PM

#2

are you using the wr or yz cams?

  • NBinSD

Posted September 13, 2008 - 02:44 PM

#3

The head is a complete YZ 400 head including the cams.

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  • Alternative

Posted September 13, 2008 - 02:48 PM

#4

Which carb does your bike have? It's possible you've got the 2nd gen FCR with the integrated hot start circuit and the YZ head was designed for the 1st gen. All this means is there will be a vacuum nipple on the head (beside the carb intake) that will need plugging, otherwise it will cause a vacuum leak causing the bike to not start.
If that's not the case check your timing again, I've never had a problem timing my 426 but apparently it's easy to screw up.
If you're sure that's right try removing the header pipe and see if there is raw fuel sitting in it. I've flooded my bike before to the point where it won't start because of fuel pooling in the header. With the header off remove the spark plug and give the bike 10 or so good kicks to clear the cylinder. Put a new plug in (even plugs that seem to be fine can still cause the bike not run) and header back on and try it again.
If it's still a no go I'd start looking at the carb, pull it a part and clean all the jets and orifices thoroughly will compressed air and carb cleaner.

  • 1rkcooper

Posted September 13, 2008 - 09:09 PM

#5

When my 98 WR was rebuilt I used a YZ head and also gave the mechanic the YZ cams and didn't think to tell him. He couldn't get it to run right and knew about the head being from a YZ and wanted to know if the cams were the ones from the YZ as well. He said the WR will not run properly using the YZ cams and WR ignition box. I gave him the WR cams and it ran great. I never gave it a second thought when I gave him the head and cams.

  • Birdy426

Posted September 15, 2008 - 02:07 AM

#6

When my 98 WR was rebuilt I used a YZ head and also gave the mechanic the YZ cams and didn't think to tell him. He couldn't get it to run right and knew about the head being from a YZ and wanted to know if the cams were the ones from the YZ as well. He said the WR will not run properly using the YZ cams and WR ignition box. I gave him the WR cams and it ran great. I never gave it a second thought when I gave him the head and cams.


Not true. YZ cams and WR cams fromt he 400s and 426s are identical...only difference is timing. Many WR folks set up their cams to YZ timing to give a more aggresive mid range hit.

One thing to check besides cam timing...If you had the slide out of the carb, make sure it is put in in the right direction. On first look, it looks like it should go in one way, but in reality goes in the opposite way. Look at the pics in the book. if it's put in backward, the bike will pop like it wants to start, but will be so lean that it will never fire. yes, I made that mistake! As stated earlier, also be sure that the vacum nipple just below the intake is either connected for a first gen FCR carb, or capped for a second gen carb.

  • NBinSD

Posted September 15, 2008 - 05:56 PM

#7

Well it was the vacuum nipple. I capped it and put on a clear fuel line so I could be sure fuel was flowing and got it started about 2 kicks later.

I'm in the procss of switching my paddle out to a knobby and then I'm going to be able to test it out!

Thanks for the help!




 
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