04 WR450 carb pilot jet question

6 replies to this topic
  • 74dirtdown

Posted December 23, 2011 - 04:16 PM


2004 Yamaha WR450

The bike was running a little rough so I decided to clean the carb. Now I haven't actually removed the carb 100%, just removed the front and back clamps in order to twist it to the side and remove the bowl.

I removed all the jets to take a look at them and clean them, but I noticed when I removed the pilot jet (the one with the little side holes all in the end) it sort of looked like it had a little black gasket (worn)around the middle of the pilot jet. I also noticed that one of the little side holes had a piece of what I think is some sort of rubber gasket in the hole.

All of the stuff I have looked at for other pilot jets, do not have any gasket looking thing. I am really just looking for someone to say, "hey you don't need that.... remove it." or "yeah that is the so and so and it needs to be replaced."

Also what would be a ball park number of twists out for the air mixture screw. I removed it before screwing it in and backing it out, so not really sure where mine was. I am just looking for a ball park on number of turns out. 1, 6, etc...? I can adjust once I get everything running.


Edited by 74dirtdown, December 23, 2011 - 04:17 PM.

  • 2grimjim

Posted December 23, 2011 - 08:58 PM


There is no o-ring or gasket with the pilot jet. Probably dried fuel residue and dirt.

Correct idle screw adjustment will be 1-3 turns out.

  • MANIAC998

Posted December 24, 2011 - 03:56 AM


Kevin, There should be nothing in there. Remove it! Some people say you can never really clean them all that well, and should be replaced. I personally clean them. I just use a piece of wire from a wire brush and work it thru the pilot a few times until it's clean. As far as the air/fuel screw setting goes, I would start at about two turns out from lightly seated. This should get you in the ballpark. An adjustable aftermarket one is highly recommended, because as you can see, it's nearly impossible to get a screwdriver in there to adjust the stocker. Maniac

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  • 74dirtdown

Posted December 24, 2011 - 06:06 AM


Well that is actually great news. It is always nice when something isn't working and you take it apart and find something wrong with the picture. As you can imagine if I was thinking it was a gasket or bad o-ring.... it wasn't good. :bonk:

Thanks for the help.


  • beezer

Posted December 24, 2011 - 07:58 AM


Next time you can try acessing the MJ and PJ through the bottom of the float bowl plug.

I use a make mirror on top of the cases to see what I'm doing.

An adjustable fuel screw is a really good idea.

Get one of the ones with the cable attached that mounts to the side of the float bowl.

  • 2grimjim

Posted December 24, 2011 - 11:32 AM


Next time you can try acessing the MJ and PJ through the bottom of the float bowl plug.

I use a make mirror on top of the cases to see what I'm doing.

I just lay the bike on its side. You can get to everything fairly easy that way, and you don't need a mirror.

  • imwaldo

Posted February 02, 2012 - 05:46 PM


...not to say that you have it, but little rubber particals and crap contaminating your carb comes from ethanol in fuel...breaking down gaskets, seals, etc. Just putting that out there!


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