Replacing Needle Valve Seat


8 replies to this topic
  • mjslim

Posted January 21, 2007 - 09:59 PM

#1

I have an '03 WR and recently my float has been sticking on occasion, so I pulled the carb off to have a look. Was expecting to find some dirt and varnish, but was perplexed when I pulled off the float bowl and the inside was as clean as a whistle. The rubber tip on the needle only has a very slight witness mark where it seals, so slight it is hard to see unless you hold it just right under good lighting.
Since I went thru all the trouble to pull the carb apart, I figured why not just replace the whole needle valve assembly and be done with it, but I have a few questions:
  • How do you get the seat out of the carb? It doesn't have a slot or hex feature like the jets - is it pressed in?
  • In searching this topic, I read other posts where people referred to replacing the O-ring in the seat. My setup appears to consist of a rubber-tipped needle and a hard (brass) seat - am I missing an O-ring?
Any help with these questions would be greatly appreciated, my thanks in advance :lol:

  • Fullbore4

Posted January 21, 2007 - 10:19 PM

#2

sounds like your valve may be okay......the brass seat stays in....i would check for adjustment of float and make sure all vent lines are not plugged.....my 2 cents.....remember float dimension is measured when float is at intermediate position (ie. not all the way out or in)

  • fourfitty

Posted January 23, 2007 - 01:45 AM

#3

I have just replaced my float needle, it seemed a bit rough on the edges and slightly sticking and the thing was flooding trying to start. I had to ride with the more than 1/4 throttle. Now that I replaced the needle I have solved the flooding but now it wont start!!!! bugger..

  • jbrooks26

Posted January 23, 2007 - 03:49 AM

#4

On the 02's the brass seat comes out and there is an o-ring on the outside of the seat that holds it inplace. That is if I remember correctly, both the needle and seat can be replaced, you have to get some sort of pick to remove the old seat though. Hope this helps.

Josh

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  • SXP

Posted January 23, 2007 - 06:58 AM

#5

I have an '03 WR and recently my float has been sticking on occasion, so I pulled the carb off to have a look. Was expecting to find some dirt and varnish, but was perplexed when I pulled off the float bowl and the inside was as clean as a whistle. The rubber tip on the needle only has a very slight witness mark where it seals, so slight it is hard to see unless you hold it just right under good lighting.
Since I went thru all the trouble to pull the carb apart, I figured why not just replace the whole needle valve assembly and be done with it, but I have a few questions:

  • How do you get the seat out of the carb? It doesn't have a slot or hex feature like the jets - is it pressed in?
  • In searching this topic, I read other posts where people referred to replacing the O-ring in the seat. My setup appears to consist of a rubber-tipped needle and a hard (brass) seat - am I missing an O-ring?
Any help with these questions would be greatly appreciated, my thanks in advance :lol:


I have an 04 carb on my WR400. The seat in the carb is pressed in. I went through the same thing as you. I changed the float, needle valve, adjusted float height and the damn thing still leaks. So the only thing to change is the seat and I can't figure out how to get it out. Also, I don't see it sold as a separate part on Yamaha's web site:excuseme:

  • GCannon

Posted January 23, 2007 - 10:41 AM

#6

Wait! The seat is held in by a screw and washer remove the screw and pull the seat straight out the o-ring is holding it in tight. there is a seat, an O-ring,and a screen, you should change them as a set. The stealership gets $47 to $50 for the needle and seat kit (try the TT store).

I have found that the needle and seat look good when I am having leaking problems. I belive the problem is that the spring in the needle looses tension and can no longer shut off the fuel before the carb bowl drain comes into play. By setting the float level slightly lower to compensate for needle spring tension the float can now apply more pressure to the seat and stop the flow.

This worked well for me since replacing a needle and seat that looked otherwise perfect was making me feel like I was missing something.

OMT when cleaning the carb make sure float hinge and needle clip are clean shmegma on these parts may lessen the float force on the needle.:lol:

  • SXP

Posted January 23, 2007 - 12:09 PM

#7

[quote name='GCannon']Wait! The seat is held in by a screw and washer QUOTE]

The design changed from 03 on. The seat is now very solidly pressed in - no screw or washer holding it in..

  • GCannon

Posted January 23, 2007 - 12:25 PM

#8

Thanks I bet Yamaha saved a bunch of $$$ on that mod. That o-ring seems to hold it in pretty tight.

  • mjslim

Posted January 23, 2007 - 09:14 PM

#9

The design changed from 03 on. The seat is now very solidly pressed in - no screw or washer holding it in..


Thanks SXP for confirming my suspicions - I was beginning to doubt myself. I think I'll take GCannon's advice and tweak the float height up a tad and see what happens. I'll hold off on replacing the needle valve for now, the TT OEM Store sells the needle for $22, but they want $12 for shipping and handling
And thanks again to all who responded - it's guys like you make this site a such a great resource :lol:




 
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