yz400 carb

4 replies to this topic
  • WR250R2017

Posted April 09, 2008 - 10:13 PM


i just bought a 99 yz400 a few days ago and fell i got a pretty good deal on it and probably because the previous owner couldnt get it started. the bikes been sitting for a few years with gas in the carb and turned to varnish and gummed everything up but thankfully from reading past posts iv been able to get it cleaned out and now the bike will start and run but it wont idle iv tried adjusting the fuel screw every which way and and the idle screw but still nothing. what ive narrowed it down to is that the fuel screw passage way must be clogged.
any tips on how to clean it out or does anybody have any other ideas on what it could be ?

  • Qwik Gixxer

Posted April 09, 2008 - 10:52 PM


Buy a can of B12 Chemtool carb cleaner and soak the entire assembly (Dismantled) in the stuff. I have had good luck doing it that way.

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  • DeeCee

Posted April 10, 2008 - 12:12 AM


I brought my YZ400f under similar circumstances last year i.e. the bike had been left standing for some time with fuel still in it.

It just took a long time to get the jets and passages in the carburettor clean so just keep at it.

The bike now runs strongly and starts first or second kick every time and idles smoothly.

I also recommend you flush the fuel tank because chances are the filter on the petcock is also blocked and there is some lumps of jelly floating around in the tank just waiting to cause problems later.

Finally, take out the choke and hot start and make sure they are clear and functioning properly (especially the hot start - make sure it closes fully and shuts off).

  • WR250R2017

Posted April 10, 2008 - 07:18 PM


im sure the hot start is working cause i took it off and blew threw it but the choke whenever i pull it out it wont stay out it just goes right back in

  • Qwik Gixxer

Posted April 14, 2008 - 08:17 AM


I have the same issue with the choke on my YZ400. Takes a couple of tries to get it to stay out.

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