1998 yz400


4 replies to this topic
  • ironmanyz400

Posted December 02, 2009 - 08:38 AM

#1

Hello. Just bought the bike. it runs well but when it gets to the upper rpms it acts like a governor is restricting it. I asked Yamaha about it and they said they do have rev restrictors but it seems this one is either set too low or it may be another issue. Looking for some direction thx.

  • glentron

Posted December 07, 2009 - 10:55 PM

#2

You probably have a bike that hasn't had the throttle stop removed. The black box on the right hand side of the carb has two bolts 4mm allen that hold the cover on. One is back deep, so don't miss it and brake the cover.

You should see a pin or throttle stop that stops the carb from opening completely. It's threaded and you have to remove it to get the power that your bike really has. Your bike will come alive if you remove it. Use a 7mm open end wrench of good needle nose pliers to remove. Let us know what you find.

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  • byggd

Posted December 08, 2009 - 03:20 PM

#3

If it's a yz400 I don't believe the throttle stop is the problem. In addition you don't want to remove it, just shorten it.

  • pablo83

Posted December 09, 2009 - 02:55 PM

#4

Hello. Just bought the bike. it runs well but when it gets to the upper rpms it acts like a governor is restricting it. I asked Yamaha about it and they said they do have rev restrictors but it seems this one is either set too low or it may be another issue. Looking for some direction thx.


Can you give some more info. Does it cut out or just kind of loose power? Does it backfire? Have you had a look inside the carb yet?

  • ArcticWR400

Posted December 17, 2009 - 04:09 PM

#5

YZ's don't have a very restrictive throttle stop that I know of it's the WR that requires you to shave the 20 something mm stopper down to 12.5, isn't it?




 
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