Carb Jetting Report

After changing main and pilot jet I was still not happy with the starting of my new WR. Went to the shop today and picked up a starter jet from the YZF. Boy what a difference. This is what I ended up with:

Main #160

Pilot #48

Starter Jet #72

Needle stock

Fuel screw 1&3/4

Acc. pump timed to one second of squirt

Grey wire unhooked

Boy what a difference a day makes. The bike now starts great and rips from off idle to w.o.t.. For those questioning the jetting choice the starter jet is the same as the YZF and the main is one size down because of the difference in needles. At this point I feel I have come up with a great combo. Anyone else who comes up with something let us know.

On to the other hot topics my clutch and starter are doing fine.

Did the shop do any jetting changes or just leave it the way it came? What is your elevation there?

Glad to hear it! Thanks for the great info.

I did all my own jetting and I am at about 500' altitude. I ride from 0 to 5000' and once I have my jetting right I rarely have to change anything. Hope this helps!

Thanks for the report! I have never heard of the accelarator pump being timed. What does this mean and how do you do it?


utvols -

Did you leave the needle clip in the stock position ??

Also curious on the accelerator spray timing as well. How do you do that ???

Did you mean that "the main (that you used on the WR)was one size down" from the YZF stock Main jet settings ??

Sounds like you really have this down. Thanks for the input !!

Rainman WFO :)

Accelerator pump mod is referred to here as the "BK" mod or the "GB" mod do a search or i think the pics are on the Motoman site on the front page.

Have you tried a YZ needle?

I'm not sure, but I think for '03 Yamaha continued the practice of shipping WRs w/ a D taper needle while the YZ gets the E.

I hope they do come with different needles, cause that means you can probably get even more power!!!.

I hope one of you lucky boys with 450's start playing with cam timing and needles and letting us know whats going on in that carb before too long.

All this "woodruf key" talk is starting to get me down.


Rainman WFO

Needle clip is in stock posistion (4) and the main was switched to a #160 as opposed to the YZ stock jet of 165. I chose that because of the difference in taper of the stock WR needle which is much leaner than YZ.

If you cant find a BK mod post here is a short and dirty version.

1) remove the carb from the bike and leave the gas in the float bowl.

2) Looking through the carb from back to front you will see a small brass needle sticking up right in front of the slide.

3) Making sure that you point the front of the carb away from you and keeping in mind that you are about to shoot gas across the floor turn the throttle wheel (brass wheel that you disconnected throttle cables from) and time how long gas shoots out of the opening. You should see about a one second squirt of fuel.

4) If this is not the case look at the throttle wheel and you will see a small phillips screw with a sping on it pushing on a black actuator. Turn this screw in to shorten duration and out to lengthen.

5) do not be suprised if this is already right. This is just another step in getting your carb adjusted right. The maunufacturers seem to be getting much better with this. I have done 4 Ktm 450exc and two were perfect and two were way off compared to older bikes always being off.

6) make your jetting changes and reinstall the carb. ENJOY Your Bike.

Hope this helps

Great job on the jetting - thanks for the report. Which jet is the Starter Jet? I talked with my shop and they didn't have any jet listed as the starter jet. They had a leak jet, pilot air jet, and MA jet. Do you know which one is the Starter jet?

Thanks, Jeff


pull the float bowl off and look at the main jet. There is a white plastic housing around the main jet. To one side is the pilot jet and on the other is the starter jet. The manual does not list options but the schematic shows the location. I just used the YZ jet and it works fine.

Thanks a lot - I will follow your lead and jet mine the same. I just got the call from my dealer - MY BIKE IS IN!!



hello utvols from a fellow tennessean. could you tell me how to do the grey wire modification on the 450. i don't know which wire, where it is, or what to do, but i want to get the best performance out of my bike. at your conveniece please tell me how to do this mod. thanks.



Pull the tank off and follow the harness from the CDI down to the group of plugs under top down tube of frame. There are two 6 pin plugs located there. You are looking for the one that is clear plastic. The grey wire was located in this connector on the bottom row center. Unplug the socket and from the CDI side of the plug I took a pair of needle nose pliers and gently worked the wire with the prong attached out of the socket. Tape this wire off completely so it can not groung to anything and plug socket back together minus the grey wire. You are done! At this time it is a good idea to silicone all your plugs were wire connect into the socket. This is not absolutely required but is a quick and easy method of further protecting your electrical parts.


Have you made any other mods to the breathing end of your bike? IE snorkels off or baffles out? I'm at the same altitude as you here in PA and am set to carbon copy your rejet.



utvols & all TT'ers -

I mirrored the settings that utvols has recommended in this thread and I can say first hand now that this is the right stuff. I did all the jetting changes and accelerator spray timing verification (it was right on from the factory), including the grey wire disconnect, and the bike has COME ALIVE !!! Now were ready to have some FUN !! :D

Good job utvols and thanks again for your post !!!

Rainman :)

Thanks for the post. Bought my bike yesterday and got the 160 main, and 48 Pilot. They did not have the 72 starter so I ordered it. Will be putting jets in today. took the rear linkage apart, and grease looked pretty good to me. Ordered my springs and should be in thursday. Will put everything back together then, and take my first ride. Boy I hate the waiting! :)


Do you know what # starter jet your WR450 originally came with?

Needle clip is in stock posistion (4) and the main was switched to a #160 as opposed to the YZ stock jet of 165. I chose that because of the difference in taper of the stock WR needle which is much leaner than YZ.

Technically that is correct, the WR needle has a "leaner" taper, but in practical terms it is probably too simplistic to say it is leaner.

I live/ride at 4,500 ft. and have two riding buddies w/ WR 426s. This altitude requires leaner jetting in every bike I've seen, but the E taper in the WR 426 was a huge improvement over the stock D taper needle. The stock WR 426 jetting, once uncorked/uncovered/unstopped, was too lean on the bottom, too rich after that, but pretty close on the main. In short it was hopelessly confused. If you haven't guessed I'm not a big fan of the D taper needle or WR jetting in particular.

This may not be true for the 450, but once you unrestrict the WR I would think it would be worth the twelve bucks to try the YZ needle (what's good for the goose...).

My two cents.

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