Jetting WR450 05

Hey guys,

I am a new german member in this great forum and now I need your help :lol:

I have got my new European WR450 05 a few weeks before and now I am trying to rejet it for better throttle response. My setting is as follows:

No grey wire modification (do I have to...?)

baffle removed

AIS removed

installed YZ throttlestop,

Airbox is stock.

PJ: stock 45

MJ: stock 165

Needle: JD red#4

Temperature: 60F - 70F

Height: 1500 feet

Now I have a terrible stutter when riding constantly at about 55mph. Response and acceleration is fine. Before I used this setting I tried the JD blue, 48 PJ, 168MJ and 170 MJ. But all of these settings did not work properly on my bike. I am wondering why my setting is so differen from yours :banghead:

What I would like to try now is to lower the needle to Clip #3, but I have fear then to be to lean :banghead: The colour of the spark seems to be ok, so the MJ shoud be allright. But what about 1/4 to 3/4 throttle....

Lots of questions.... can anybody help?


I would do the grey wire mod, apparantly it remaps the ignition for use with the yz throttle stop. Also you should search on "stumble when cruising" on this forum. It seems like quite a few people have experienced this. I have never felt it on mine but I ride tight woods and logging roads so i'm almost never cruising. You should also do the airbox mod. it probably doesn't have anything to do with your problem but it lets it breath better.

Thx dan,

I will try the grey wire mod, but I am not shure if it works on the European WRs. There is a grey wire but if it is grounded :banghead: , didn't check it up to now.

Does the grey wire mod affect the jetting to lean or rich?

On the other hand I can't understand my complete different lean ( near to stock) jetting with the JD Kit. Most of you and the JD instruction indikate richer settings :banghead: Can a lean setting of the needle be critical to the engine or do I only have to be careful with the mainjet?


Try JD blue needle in clip #4 & a 48 pilot.

Check your hot start lever cable for slack. It may be to tight and hanging open causing your jetting problems. I have a JD red needle, clip #3, 48 pilot with a 170 main in my 05.

Ok here some results of my tests in history:

- firts I tried as suggested JD blue at #3 with MJ 170, PJ 48: it was terrible rich rich on high and low rpm, was stuttering on accel. and had a bog on 1/8 to 1/4

- changed setting to JD blue #3 MJ 168, PJ 48: high rpm becomes better, no reaction on changes on the fuel screw

- changing setting to JD blue #3 MJ 168, PJ 45: accel on low becomes better, some reaction on fuel screw, when nearly closing the screw

- changing to JD red #5, MJ 168, PJ 45: bog becomes better, at high rpm bad accel

- changing to JD red #5, MJ 165, PJ 45: minimal bog on quick accel, some stutter on high rpms

- changing to JD red #4, MJ 165, PJ45: minimal bog, stutter as described on top, when pulling the hotstart lever the studder goes away

- the grey wire is grounded on my bike, but disconnecting it doesn't change the timing or something else, so I let it stock

- I will let the airbox closed, because next weeks I will ride in very fine sand an I can not change the airfilter every hour


why should i change to PJ 48 and JD blue #4? Wouldn't this rich the setting on the lower/ mid end. I think the studder comes why I am to rich?

I tried for test the original Yamaha OBDUS Needle on #4: nearly no studder, minimal bog on low, but the engine feels more rough then with the JD needle

The setting with the Yam Needle + the smoothness of accel with JD Needle would be perfekt.... any ideas


good idea, I will check start lever cable

Thx @all

I am not sure why your bike is running so rich down low?

If you run better with a 45 pilot, and stock needle I suspect you have poor air flow into your airbox. Most of the TT members have modified the flow into their airbox with the other mods you listed. Your exhaust is uncorked so you might want to punch out the air holes on the right side of the airbox and put small filter foam plugs in it. :banghead: you might want to punch out the air holes on the right side of the airbox and put small filter foam plugs in it

Perhaps I will try after my desert trip in a few weeks.... but I tried the suggested JD jetting with also on the left side opend airbox, which made no differences except that it was loud :banghead:

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