2002 yz426 with 2001 carb. Found small emulsification tube in bowl? where does it go?

6 replies to this topic
  • tompo426

Posted September 13, 2011 - 02:54 AM


I have a YZ426 2002 with a 2001 carb on it. I was servicing the carb when i came across a small, holed emulsification tube. It looks like it sat under the starter jet but when i have a look at exploded digrams there is no mention of the tube. It is about 3/4 inch long, 1mm-2mm in width with a taper at one end ( as if it was to be seated into an orrifice). the only place that seemed to fit the criteria was underneath the starter jet. It is presently fitted under the jet.
My bike has very erratic starting...it will fire up from cold no problem but as soon as it has a bit of heat in it, it wont play ball 70% of the time. BUT, to throw a spanner in the works there is no pattern because its a hit or a miss when it decides to start or not.
Any help would be appreciated as i'm starting to lose the battle with the bing :)

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Edited by tompo426, September 13, 2011 - 04:10 AM.
forgot to mention you tube handle

  • tompo426

Posted September 16, 2011 - 02:38 AM


Found where it goes. My mate has a yz400f and the carb on his bike had the same tube. It sat under the starter jet...jobs a good 1

  • Mr. Neutron

Posted September 16, 2011 - 04:21 AM


Once you got it back where it's supposed to go, does your bike run a little better?


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  • grayracer513

Posted September 16, 2011 - 07:09 AM


The starter jet is only active while the choke is in use. It's also likely that if the tube comes free of the carb with the jet in place, that there is nowhere for it to go.

  • Mr. Neutron

Posted September 16, 2011 - 08:07 AM


Thanks, Gray!

I was actually having a kinda tough time getting a good "visual" of where this part had come from.....


  • tompo426

Posted September 25, 2011 - 05:03 AM


aaaahhhhh....i could cry if i hadnt already dehydrated myself trying to start the bike.
A wee update, its definetly the starter jet, if you have the haynes book number 2689, titled yamaha yz & wr 4 stroke motocross and off road bikes '98 to '08, on page 4.16 picture 5.3i.... i can actually see the top of the brass tube im talking about as the starter jet is removed in the pic. My problem is that i cant find any mention anywhere of this tube being an item that should have been removed.

the other thing ive noticed is the guy i bought the bike from had put it on the road and the carb had been messed about with previously because of the road legal can that went on.
The manual says my pilot screw should be out 1 - 1/4 turn out.....the bike wont start at all with it at these numbers, however if i have it between 2 and 2.5 turns out it behaves much better.
all the jets are the correct size and the accelerator pump works without hitting the throttle slide....the only other thing is that i constantly have to adjust my idle screw to keep the tick over from climbing too high.

I had the bike out yesterday and the bloody thing is still behaving bonkers

  • tompo426

Posted September 25, 2011 - 05:09 AM


sorry for being a pain guys but i noticed my cold choke (black knob) shaft has a slight bend in it.... are they supposed to be like that to allow the knob to clear hitting the hot start knob (red knob) ?.....or could that allow a small air leak i.e. drawing air? the bike rides fine.
it seems as though its pilot circuit troubles because as soon as the bikes throttle is past about an eigth to a full i.e. by the time its onto the needle and main circuit its flying

Edited by tompo426, September 25, 2011 - 05:47 AM.

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