Carb needles & pilot/slow jet

11 replies to this topic
  • Jackazz

Posted December 13, 2004 - 01:01 PM


Has anyone tried using the standard YZ needle in their WR? I'm looking to fiddle with my jetting a bit more & was curious. I know most on here preach the JD kit, but I can get a YZ needle (or any of about 20 YZ or WR neeldes) for $9.95 + s&h from & I'll be ordering some other stuff from them anyhow.

Also, regarding the pilot or "slow" jet, WR stock is #45, YZ stock is a #42, & it seems I've heard alot of people going to a #48. Curious as to who's had what kind of results with what.

I ride in MO, so elevation is probably any where from roughly sea level to maybe as much as 1000ft. Hot & humid in the summer, cold & dry in the winter.

Thanks Guys,

  • Texas4play

Posted December 13, 2004 - 02:43 PM


I've read a few posts on here that a YZ needle works or you can use an earlier model (03/04) WR needle (if yours is an 05 - no adjustment).

Bumping the pilot jet would only be needed if your fuel screw has to be turned out too far (approx 2.5 + turns out or more)

  • WR450F_RDR

Posted December 13, 2004 - 03:03 PM


I would only suggest bumping your pilot jet up to a 48 if your using after market exhaust which will uncork the bike and let it breath easier, otherwise there is no reason to use a bigger jet, even when I was running an pro-moto insert I didnt change the pilot. I am currently using a FMF Powercore IV and like the results, turns the WR into monster.

  • mtrablue

Posted December 13, 2004 - 04:35 PM


man, i sure wish you'd call me with this stuff.

if you have an '03 wr, the '03 yz needle is a big improvement. the '04 wr needle is better than the '03, but the '04 yz is worth trying. if you run the 45 pilot and you back the pilot fuel screw out to three turns, you need a 48. now that it's getting cold, a 48 is not a bad idea anyway. the yz uses a 42 pilot because it doesn't have the acv (air cut valve) system we have. it's the little round cover on the side of our carbs.

i'm running a 48 pilot, 100 pilot air jet, blue jd needle (clip in the middle), 40 leak jet, and a 165 main. air box is opened up a bit and i use a gytr insert in the stock can.

i rode yesterday morning at about 40 degrees and the bike ran great. by the way we're at about 650 feet above sea level. when are you going to ride next?

  • Jackazz

Posted December 14, 2004 - 08:08 AM


Hey Alan! Yeah, I always forget to seek out the locals who've done this stuff first... :cry:

Have you tried disabling the ACV? Just curious. Also, you said you're running a 100 pilot air jet & a 40 leak jet, did you change these out or did it come that way? I'm not sure what you mean by "leak jet" though. I scanned the carb pages from my manual to have at work for reference, & couldn't find the term leak jet on there so I wasn't 100% sure what you were talking about. Care to have a look at these pages from the manual or this exploded view from Yamaha's parts finder & let me know what's up?

Not 100% sure when I'm going riding again, scheduling is starting to get hectic. I was supposed to be at St. Joe on Sunday, but missed out due to some scheduling conflicts & mis-communication. :cry: I might wind up having to wait until mid-January unless I can figure out how to break away this weekend.

  • Jackazz

Posted December 14, 2004 - 03:12 PM


I'm bumping this back to the top of the page in hope that you see it MTRABLUE... :cry:

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  • Robert_Brazil

Posted December 14, 2004 - 03:26 PM


I ordered today the YZ exhaust cam to modify my WR into a YZ timed beast, Question: should I need to change the carb needle too, and if so which one? T :cry: he Yamaha manual shows SEVEN! models (YR, YS, JN, JP, J1, JR and JS) , what comes stock in the YZ?

  • mtrablue

Posted December 14, 2004 - 09:26 PM


i'm sure you saw the other stuff on the acv i responded with. i type so slow i won't try to rewrite it. if you look in the owner's manual ("ENG" section) for the carb blow up, you should be able to see the leak jet. it's located in the bottom of the float bowl. the '03 manual has it as number 14.

the pilot air jet and leak jet are changes i got from here on tt. the leak jet is part of the accelerator pump system. the leak jet "bleeds" some fuel from the pump squirt. the newer WR's tend to be a bit lean off idle. the smaller leak jet gets more fuel into the the squirt. it helps get rid of the off idle bog. '03 had a 70, not sure about '04. that should be in your "SPEC" section in the front of the manual. 100 pilot air jet is what the yz's run. that and the 48 pilot jet help to round out my low speed jetting.

if you need the numbers;
40 leak jet 4JT-1494F-03
100 pilot air jet 5TA-14943-27

i'm off work for two weeks starting friday. if you get a day , let me know.

  • Treebark

Posted December 15, 2004 - 07:42 AM


Are you going riding this weekend(17-18th)? I can get away for a day if you want to go riding let me know.

I had the same thought of using YZ needles after I bought the JD jet kit. I was disappointed to see that the kit only came with 2 needles and 4 main jet that I already have. If the kit came with main, pilots, leak,pilot air jets it would be worth the money. I would buy the YZ needles and see which works best. You can get almost all of the YZ needles for the same amount of money. I went ahead and used the JD blue needle on the 4th clip and bike does run great.

I have had that off idle bog since I put a YZ pipe on and took mtra advice and put a different leak jet in. First I put a 50 leakjet in and it did take care of the problem then I tried a 40 leakjet to see if it made any difference and it does hit a little harder. The leak jet is in the carb bowl and the manual doesn't mention it but is listed in parts manual.

I did try a 48 pilot jet without using a 100 pilot air jet and made the bike run worse. If you do go to a 48 pilot you must change the air jet to a #100 and it makes a big difference in mid range response.

I was running a 175 mj before all the changes and the bike ran good but could smell the rich mixture out of the exhaust. I changed the main to 170 and the smell is gone but now what I noticed is that the bike is still a gas hog. I have a 3.4 gal and use to get 3 rides(30-35miles) on a tank and now I'm hitting the reserve at the end of my second ride. I will try using a 168 or a 165 main to see if it improves mileage without sacrificing response.

Part info
I researched jetting part numbers and listed them on a thread "jet part numbers " which are correct. I bump the thread up today so check out the part numbers and pick the ones you want to use. The pilot air jet and main air jet numbers are the same thing. Use the 5TA numbers they are the ones to use, the other air jet numbers are for the 250f but will work.
Try this place for parts they are a little cheaperZanotti Motors Home Page . They don't have a microfiche to look up parts but if you get the part numbers you can type them in the part search page and they should beat anyone's price.

  • Jackazz

Posted December 15, 2004 - 08:04 AM


MTRABlue & Treebark, thanks for the info guys. :cry: :cry:

I need to add you guys to my "buddy list" or whatever so I can remember you guys are "in the neighborhood" & have pretty well allready figured your WR's out.

So, now that I'm getting all this jetting straightened out...

Have either of you guys messed with your accelerator pumps? :cry:

  • Treebark

Posted December 15, 2004 - 08:22 AM


I have readjusted it and put the leak jet in and that's all I've done. The adjustment is in the manual. It's fairly easy and found that it was only slightly out of adjustment and didn't notice a change. The method is to unscrew the idle stop and remove the cover on right side of the carb, remove the boot from air cleaner to carb, open the throttle place something under the throttle plate of the thickness stated in the manual, I used a allen wrench , then adjust the screw facing the front of the bike until slack is gone. This is just off the top of my head and not sure on the specifics. check in the manual.


Posted December 15, 2004 - 04:36 PM


I just put a YZ needle in my '05. Honestly, I put the circlip in a position (4th I believe) equal to the stock position just to see if the bike would be ok. It runs like stock so i will drop the clip when I work up the motivation and report back. :cry:


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