Off my WR426 and onto WR450 - 1st thoughts and Qs

As I recently posted, I just got a semi used WR450, a few months after my WR426 got too warm to ride.

My 426 was YZ timed, jetted, blah, blah, and was fast out of the hole and on the top end. Way fast, with a big hit to get you there, too.

The WR450 feels... sluggish. There is no hit. It is weak down low and the top end is not impressive. Going 20mph on the 426 I could be in 2nd, 3rd, 4th, didn't matter and wheelie with a twist. On the 450 I have to be in the right gear or no dice. Even then it's harder. However, I can climb a hill incredibly slow on the 450 and NO STALL. The 426 couldn't brag about that. It stalled if you looked at it funny.

I'm also having a problem while I'm putting around and suddenly give it full throttle. The bike chokes, almost dies, and then picks up and goes a second later.

I need to talk to the original owner to figure out exactly what jetting and other mods he did, and then I'll get back to you guys. I expect some help here, too. Everyone got a good giggle out of my burning motorcycle story; that should be worth some free advice. I gotta get this bike hopped up.

Thanks! :)


I had a WR400 before my WR450. The 400 I had YZ timed with all the other free mods and loved it. I think that my 450 has better power even though it's WR timed. I'm curious to see what mods have been done. Then get your jetting dialed and see if your still not liking it. You could always think about a YZ cam, then it will hit like a ton-o-bricks

The dealer had already removed the baffle, cut the throttle stop and jetted mine. After about 500 miles

I had the YZF cam installed, installed a power now and

cut the grey wire -it gets up every hill my modified 98'

KX500 did! It also easily pulls 5th gear wheelies. Enjoy!

Stock the bike is poorly jetted and choked up.

I changed the jetting and cut the grey wire and put in a ProMoto exhaust baffle. I also removed the intake baffle in the airbox.

The bike is very fast and starts easily.

Guys who need big horsepressure use YZ parts.

I think I would buy the JD jetting kit.

With 2 hours of work the bike will really run.

Get busy! :)

Alright guys, as far as I can figure out, here's what the original owner did (in my new and improved signature) to my slightly used fo-fitty.

So, couple questions:

(1) Quick goose at low RPM kills the motor. Any suggestions?

(2) If I take the PMB insert out I get a ton more power. Am I really going to have to give up that much power to keep quiet OR will the effect lessen with a properly jetted motor?

(3) YZ timing... worth it? I understand you have to buy new cams. It seems as though folks change the exhaust... what about intake?

(4) What mods am I missing?

I miss my 426.

C'Mon guys... someone can answer at least #1 (and perhaps #4). Thanks.

Proper jetting will bring out the life. For question #1, check the accelerator pump squirt duration. It should only squirt for less than a second. If it squirts for longer, do the BK mod and that will definatly help with the issue. I would also recommend buying the JD jetting kit from the TT store. I am guessing that it has the stock WR needle in it, changing it out with the JD kit needles will make a huge difference in performance. I don't know what to tell ya about the quiet insert except California sucks! I guess you could try to find a quiet aftermarket exhaust. Have you opened up the air box? I read somewhere on TT that a guy replaced the battery with a small battery pack so he could remove the whole airbox lid. Hope this helps.

I am not an expert on jetting but i would say your pilot is to rich. To fix my bottom end bog I bought the jd jetting kit. Does it ever work good no more bog and a way stronger mid range. Can easily loft the front tire over a log in third with a blip of the throttle, also I was taking off and not sure of what gear I was in 3 gear i can now start off in third like it was second with 14/51 gearing. With the yz exhaust and the jd jetting I am now very happy with the perfomance of my bike very strong power through out the whole range. As for the ehuast you can get 96 db end caps that dont hender the performace that much. :)

For bog try adjusting the pilot screw, if that doesn't fix it consider the BK mod. . On my WR426 pulling the insert made a big difference in power. On the 450 it made an even bigger difference. The stock pipe without a insert is pretty good, but loud. An aftermarket pipe will give you more power but expect it to be loud also.

Graham, I came from a 98WR400,01WR426 to my WR450. I agree with most of the things you say about the power differences. The power is now much smoother than before, it's not slower.. I can tell that the insert that you have in there is not helping things out. I put a TI-4 exhaust on my bike and made a huge difference. My bike is jetted totally stock and I cannot get by bike to backfire or hiccup, I've tried.

Do yourself a favor. Hold off on the cams and other aftermarket mods, let's get your bike running great stock and then move on from there....

You only live 40 minutes away from me so stock jetting should work for you too..

Jet you bike like this:


Starter Jet:65


pilot airjet:80


clip" 4th (middle)

airscrew 1.25 out

While you're at it change the plug and totally clean out the carb......

If that doesn't work unplug your TPS and see if that helps...

If you need any help doing this, feel free to bring your bike over to me, and we'll get it perfect...

Dan :)

Thanks Dan.

Re: your exhaust... is it 96db legal or not?

I've got the stock jets... thought about that. Everyone seems to like the JD kit as well. I can live without the 426 hit, but I can't live with it stalling everytime I jump on the gas. E-starting is hard as well. A good kick works fine every time. Perhaps the E-start isn't as fast? Thanks for the advice and the offer to help. I've never changed jets...

your exhaust... is it 96db legal or not?

Nope.... If you need to get to 96, get the PC496 or the FMF Q....

Please don't fool yourself with the performance of your bike..... Your jetting is jacked up!! Your estart is suffering because of it.. Trust me, I've been through this with my dads 450... Just jet it STOCK like mine!!!! You'll thank me!!!!!!!!! :)

I've got the stock jets... thought about that.

JUST DO IT!!!!!!!!!!!!!!!!!!!!!!!!!!!

Stock the bike is poorly jetted and choked up.

Not my bike Beezer...... My bike came perfectly jetted and didn't come with a grey wire or throttle stop, just a lame Canadian exhaust sys.

So is your bike Canadian, Dan? I was just going to throw my stock jets back in, but if yours is Canadian, then the jetting differs. I can still match your specs, though. Thanks.

Switched back to stock sj(65) and my stock pj(45). Didn't seem to make any difference in the stalling when I stab the throttle. I checked the squirt duration... it's about 1/2 second without the BK mod. Does every carb need the BK mod, or are some just long squirters?

Any other ideas? Given the shape of my body, and the thickness of my wallet, I don't appear to be either lean or rich.

The top end seems a bit sluggish still. 1/4 - 3/4 are awesome, but that last 1/4 (really 1/8) seem to roll on slowly. I just came off a yz timed 426 though, and it could be that that's the way the WR450s come. Any other WR450 owners have the same experience?


Do yourself a favor and buy the JD jetting kit. The JD kit is worth the money. His needles are the shizit! From off idle to the top they rock! :)

Also the BK mod doesn't apply to the WR450. The carb is new this year and differant. You might try turning the acc. pump adjusting screw clockwise a half turn. This will delay the squirt just a little and let the slide open a hair more before squirting.


Too many settings. Oh well...

JD kit is on the way, and a ZipTy fuel screw so I can fool around with that a bit more easily.

From what I understand, the accel.pump squirt is supposed to hit the slide just as it begins to move... can anyone confirm that?

Last Q for now... Is it possible to get enough air with the battery in place (and the insert removed)? I've seen 'interesting' mods with holes in the side covers, or replacing the battery with a smaller one, but I'm not going to do that if I don't need to.


I cut the left number plate opening out even though I only removed the restrictor from the airbox. It provides a grab spot to pull the back end around if you are standing on the right side of the bike. I would recommend cutting it out just for that reason. :)



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