Suggested Extra carb jets to get?

10 replies to this topic
  • dbailey223

Posted October 08, 2005 - 04:11 PM


I received the JD kit and installed the needle and main jet according to the jetting guidelines on this forum for my temp and alt (red needle clip position 5 from the top, and main jet #168).

My next step is to go the Yamaha dealer and get the other jets suggested in the guidelines (48 Pilot, 70 starter jet, #40 leak jet). As long as I am there, what are the other jet #s for the other jets that would be a good idea to pick up?

  • bg10459

Posted October 08, 2005 - 04:32 PM


In addition, I'd get a 45 and a 50 pilot jet (I think 42 is stock), 50 leak jet (I think 70 is stock), and 68 and 72 starter jets, maybe even a 75 if you ride in the winter (I think 65 is stock). The JD kit has you covered with the mains and the needles.

  • clark4131

Posted October 08, 2005 - 05:16 PM


To cover all your bases, here's what I recommend...

Main Jets - #160 thru #175
Pilot Jets - #42 - #50
Leak Jets - #0 - #60
Starter Jets - #65 - #72

Don't get them from your local dealer or you'll likely pay out the rectum. I'm a big fan of Zanotti's for the leak and starter jets as they're traditionally about half price, but you will pay for the shipping. Most independent shops will carry the pilots and mains for quite a bit cheaper as well. So there you have it...SC

  • dbailey223

Posted October 08, 2005 - 08:34 PM


Looks like according to the Shop Manual, standard for US 03 WR 450f's is main 150, pilot jet 45, starter jet 65. So, I have those plus the JD mains. I'll will gather a collection from there. Thanks!

Oh, the manual doesn't seem to show the standard leak jet and the Yamaha website doesn't show it in the parts section to get a part number. Anybody know what it is so I can look it up on Zanoti's?

And, there is no #72 or 75 starter jet on the Yamaha part website. Wazzup?

  • bg10459

Posted October 09, 2005 - 05:41 AM


The manual uses different terminology. Per the Yamaha diagram, here's what's what:

13 - Needle - 1/8 to 3/4 Throttle
19 - main jet - 3/4 to Full Throttle
20 - pilot jet (aka slow jet) - 0 to 1/4 Throttle
21 - starter jet (aka jet) - Choke Circuit
22 - Pilot Air Jet (aka jet) - Vacuum at Pilot Jet (small jet = high vacuum)
23 - Leak Jet (aka jet)- Accelerator Pump Circuit (smaller = more squirt)

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  • mtrablue

Posted October 09, 2005 - 07:45 AM


you really don't need to get a lot of extra jets unless you ride in florida (sea level) and then colorado (10,000 to 12,000 ft above). another thing to keep in mind is that not all bikes of the same year and model will be the same.

you've got a 168 main. i run a 162 main at 600 ft above sea level with a Q2 exhaust and an opened up air box (indy mod). i ran a 155 when i was in colorado in august. put in a 40 leak jet and forget it. stock starter jet is a 65. change to a 72 when it gets to around 40 degrees or below. if you run too rich of a starter jet when it's warm and let the bike run with the choke on, you run the risk dumping too much gas into the bike. i learned this when my oil started to smell like gas!

dialing in the pilot jet can be complicated. there are almost too many options. not only is there a pilot jet, but there is also a pilot air jet. not to mention a pilot fuel screw. stock (45) is too lean and for some a 48 can be too rich. the fuel screw will help some with this. some of us went to a 100 pilot air jet ( YZ ), 70 is stock. there is supposed to be a ratio of between pilot jet size and pilot air jet size but i'm not sure where you can find that. when you go up on one, you need to go up on the other. i found that with a 48 pilot and a 100 pilot air, the idle would " hang " just a little. i tried to adjust it out with the fuel screw but i turned it out to the point i was afraid it might fall out. i went to a 85 pilot air jet and all is good. in colorado i went back to the stock 45/70 combo and the bike ran great.

i do run the jd needles. i change from red to blue when i change the starter jet (temps in the 40's). clip in the middle position. i only had to drop the needle (raise the clip) one position for colorado.

i know that was probably more info than you asked for but what i was trying to show was that you really don't need every jet made. a lot of work has been done by the '03 WR owners before you. some very good base line numbers are already there. i think this forum did a bunch of the work for jd. the original jd instructions had nothing about starter jets or leak jets.

  • Matty05

Posted October 09, 2005 - 06:03 PM


There is really only 3 parts you should only have to play with. That is the needle, pilot jet and the main jet.

You have the JD jetting kit, that comes with main jets. I would just get a
#48 and #50 pilot jets if you don't have them.

I wouldn't bother with any other jets, you can really muck things up. One thing to do for sure is keep track of the jets in your carb. Keep a note in the back of your manual so you will know what you have tried and what worked for different times of year.

Unless you have a dyno and a CO2 sniffer, you just have to go on feel.
You might feel the difference between 1 jet size, you may not.

  • clark4131

Posted October 09, 2005 - 06:24 PM


If you're just going to be riding in the same place all the time, then just get what you need. I ride in Mexico on the beach all the way to over 10,000' in the Rockies so I have an entire buffet of jets...SC

  • dbailey223

Posted October 09, 2005 - 09:38 PM


I'm usually in the same place, Las Vegas, but in the Summer it can be 90 to 110, and elevations of 3,000 to 8,000; but in the winter the temps can be 40-60. So, I'm looking to get a range of jets, etc.

  • dbailey223

Posted October 09, 2005 - 09:41 PM


You guys will love this. I go to the local Yamaha dealer today to get the 48 pilot jet and to see if he has the leak and starter jets. He didn't want to sell me the starter and leak jets because he has servived hundreds of wr 450s in the last 6 months and I just don't need to change those. Turns out he didn't have them in stock, because his feelings weren't going to deter me!

Then, he gave me the pilot jet for free. Wow, what a turn around!

  • mtrablue

Posted October 10, 2005 - 03:12 PM


[quote name='Matty05']There is really only 3 parts you should only have to play with. That is the needle, pilot jet and the main jet.

that's fine if you've got an '05 but '03's were way off. most of the stuff was figured out by '05. do the 40 leak jet also. '05 comes with a 50, '03 came with a 70. big difference when you snap the throttle.


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