Need Advice For Jetting My 2004 WR450

I know this has been posted and asked a million times but here I go again. I need help with jetting my WR450. I have the stock exhaust with baffle removed, airbox mod, throttle stop mod and gray wire cut. For a while I was getting along just fine with the stock jetting but just this weekend it started to run like crap, backfiring and dieing at idle. Between acceleration and deacceleration it runs terrible! Drained the gas and put in new and still the same problem. I understand something about a rejetting kit for the WR's? What kit do I need, and where do I get one?? I'm in Arizona and the desert here is around 500ft above sea level. What do I need to do to get my WR kicking some butt! I need some numbers from you guys. I'd appreciate any feedback.

JD Jetting Kit, Zip-Ty fuel screw, 48 Pilot jet, 40 Leak jet, 70 Starter Jet and Indy's jetting chart...SC

I didn't quite understand what degrees he's talking about, is that in Celcius? Anyway, I did order the JD jetting kit and the Zip Ty fuel screw for my WR off thumpertalk. What are some good numbers to start with?

I forgot to add I've had this problem ever since I bought my WR last year. If I stable the throttle wide open is a very fast motion, the engine badly cuts out just for a second then comes to life. It does this at idle or in gear. What causes it do to that?

You're either getting too much or too little fuel for the amount of air that's going in the engine at different throttle positions. Try like SC said. I personally had better results with the 52 leak jet than the 40, but each bike is different, so trial and error is your best bet. INDY's jetting chart is a great place to start. BTW, it's degrees in Farenheit.

I'm assuming you're talking about how the engine bogs or dies if you wick open the throttle from idle, yes? The Accelerator Pump is what controls that, and you'll likely never get rid of it. First, that's inherent to 4-strokes. Second, you should never test your jetting with the bike on a stand or not moving. Third, the bike needs to be good and warm before you determine your jetting needs.

Indy's jetting chart is based off two criteria, temperature and elevation. Your settings will be in the first block of numbers. Just figure out the outside temp and set accordingly. You're undoubtedly in one of the following two ranges:

60 to 75 degrees: 170 main, JD Blue #3 or JD Red #5, 48 Pilot, 1.5 turns, 70 starter jet, #40 leak jet

75 to 90 degrees: 168 main, JD Red #5, 48 Pilot, 1.25 turns, 68 starter jet, #50 leak jet

And the temps are in Fahrenheit...Above 70 degrees Celsius you're dead :applause: ...SC

Mike, Your pilot needs to be a 48! Your Main should either be a 168 or 170, I've tried both and like the 170 better but have friends that run the 168... You're at my same elevation that I'm at, I've ridden AZ with my specs, they're perfect. If your bike ran great before and now it doesn't, it sounds like you have a dirty carb. Mine gets dirty all the time, you should clean out the carb throughly, make sure to blow out everything including the AP diaphragm area. These carbs are real finicky and need to be spotless... No real need to get into leak jets and starter jets until the bike runs perfectly..


thanks guys for all the info. Looks like I'll be going with this for a start

75 to 90 degrees: 168 main, JD Red #5, 48 Pilot, 1.25 turns, 68 starter jet, #50 leak jet

Once my JD kit comes in the mail I'll be going with those numbers. Sound good to all of ya?

Yes wants to die in idle or in gear if I punch the throttle wide open very fast.

Bump ------------

Just an FYI--if I recall right, the JD kit will not come with leak or starter jets. You have to get those elsewhere. I installed the JD kit and have not messed with the leak or starter jets because I saw big improvement with just the kit and because I wanted to wait until I got my stock baffle out. I just got my PMB insert, and get it installed.

So, over the next couple weeks, I plan to do some tweaking and to get some leak jets to see how the performance is affected.

I understand what the pilot, main, and starter jets affect, but what does the leak jet control? Thanks

The leak jet is for the accelerator pump. It controls how much fuel leaks back into the bowl when you give the throttle a quick twist. A smaller jet will allow less fuel to leak back and more to go to the AP squirt. It has little or no effect when you slowly roll the throttle.

ok since the JD jetting kit doesn't come with the starter or leak jet, where do I get those?

Yamaha. But you need to tell them the part number or they will never find it on the micorfiche! :applause: Here are all the part numbers:


4MX-14943-42-00 .JET, MAIN (#175) AP 1

4MX-14943-40-00 .JET, MAIN (#165) STD 1

4MX-14943-91-00 .JET, MAIN (#168) AP 1

4MX-14943-41-00 .JET, MAIN (#170) AP 1

4MX-14943-92-00 .JET, MAIN (#172) AP 1

4MX-14943-93-00 .JET, MAIN (#178) AP 1

4MX-14943-89-00 .JET, MAIN (#158) AP 1

4MX-14943-39-00 .JET, MAIN (#160) AP 1

4MX-14943-90-00 .JET, MAIN (#162) AP 1

4MX-14943-88-00 .JET, MAIN (#152) AP 1

4MX-14943-38-00 .JET, MAIN (#155) AP 1


4MX-14948-06-00 .JET, SLOW (#48) AP 1

4MX-14948-04-00 .JET, SLOW (#42) STD 1

4MX-14948-05-00 .JET, SLOW (#45) AP 1

4MX-14948-07-00 .JET, SLOW (#50) AP 1

4MX-14948-01-00 .JET, SLOW (#35) AP 1

4MX-14948-02-00 .JET, SLOW (#38) AP 1

4MX-14948-03-00 .JET, SLOW (#40) AP 1


3TJ-1494F-13-00 .JET (#65) AP 1

3TJ-1494F-12-00 .JET (#62) AP 1

3TJ-1494F-14-00 .JET (#68) AP 1

3TJ-1494F-15-00 .JET (#70) AP 1

3TJ-1494F-16-00 .JET (#72) STD 1

3TJ-1494F-17-00 .JET (#75) AP 1

3TJ-1494F-20-00 .JET (#82) AP 1

3TJ-1494F-18-00 .JET (#78) AP 1

3TJ-1494F-19-00 .JET (#80) AP 1


5TA-14943-27-00 .JET, MAIN (#100) 1

5TA-14943-15-00 .JET, MAIN (#70)


7A9-14943-27-00 JET (#100)

7A9-14943-17-00 JET (#75)


4JT-1494F-19-00 .JET (#80) AP 1

4JT-1494F-15-00 .JET (#70) STD 1

4JT-1494F-23-00 .JET (#90) AP 1

4JT-1494F-03-00 .JET (#40) AP 1

4JT-1494F-07-00 .JET (#50) AP 1

4JT-1494F-11-00 .JET (#60) AP 1

4JT-1494F-27-00 .JET(#100) AP 1

My local dealer didn't have em in stock (the leak and starter jets)--they would have to order them. So, I'm gonna look for a site to order online.

ok well got my JD jetting kit in the mail today. I was suprised to see that there were no pilot jets in the JD kit. What's up with that. I thought they were. Just 4 different sized main jets and blue and red needles. Is that really all that comes with the JD jetting kit for the WR450? I'm lost!

That's it. Money well spent, huh?

It is a good thing that the needles work.

yeah you got that right, I hope it works good

the jd kit is worth the money you spent. dont worry. almost impossible to get spot-on jetting without the jd tapered needles.

The jets, if the local dealer has them in stock, are like $1.08 a piece--so you can get the ones you need for not much more $.

well got the pilot jet today #48. I'm going to go with 168 main with red needle and the 48 pilot. I'll post back soon to let ya all know how well it worked.

Is it getting hotter there??? What is the temp?

I ride at about sea level to about 200'. It is really humid here and about 90 degrees.

I had to go leaner on the needle about 2 weeks ago. I am using jd red #4 clip now.

168 main should be right but you might want to try 165 as well with the stock exhaust.

GET A ZIP-TY FUEL MIXTURE SCREW NOW IF YOU DON'T HAVE ONE!!!! You have to pull off your carb to get to the stock sucker to adjust it.

You might have to go red needle 4th clip, but try 5th clip as well. You can tell the difference between them.

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