Jetting once again

O.K. I'am about ready to break down and spend the $70.00 bucks for a JD jetting Kit. I'am determined to get rid of that stutter hesitation at about 1/4 throttle. I'am at 4500 ft. got a 160 main 48 pilot I've tried the stock needle on different clips,my daeler recommended a YZ needle, which I juat installed its a NCVQ, Tried it on 4th, 6th and 3rd clip, it runs the best on 3rd clip down, but the stutter is still there. You guys that have done the JD jets, does it eliminate the problem, or just help?

What stutter? JD kit just rocks. Put in Red #4 and stop guessing and listening to dealers who dont even ride dirt bikes! :thumbsup:

the kit will help. the problem is how each owner defines the "bog". do you feel it when you ride or just in the driveway when you snap open the throttle? we're all a little differant. i've noticed that we seem to have come back to the accelerator pump for some more options. on 400's and 426's owners tried to reduce the amount of fuel squirted. 450 owners may be looking for more. the '03 came with a 70 leak jet. the '04 comes with a 60. smaller hole, more fuel through the carb. i have a 50 in my '03 and it runs great.

I live just down the road from you and picked up my wr last week. I have not really noticed the bog while riding, but just reving it in the driveway. I have noticed a little surge when cruising steady about 1/8 to 1/4 throttle. I would be curious to know what you end up doing.

I get the surging from an 1/8 to 1/4 throttle too, with the JD Kit. The JD kit helped the mid throttle. Before the Kit, it surged from 1/8 to 1/2 throttle.

I'am talking about that Surge that mparrish is talking about, the bog when you snap open the throttle does'nt bother me as much as when you are just riding along at a steady 1/4 throttle and it surges or hesitates or sutters as James Dean calls it. Thats what I'am hoping to get rid of. I E-mailed James Dean he said all the 03's and 04's do it. I think you guys at lower altitudes don't seem to have it as bad. So Indy450 are you saying you don't have any bog or hesitation at a steady throttle and was that with just a needle and main-pilot jet change or did you do that leak jet stuff?

I had the stutter 1/8 to 1/4 throttle. Installed the JD kit in the 4th clip position, still there. Dropped the needle one notch.....GONE!

Yamaharichey, surging at constant throttle is the sign of a lean condition. If needle clip positions are too course of an adjustment, try shimming the needle with thin washers.

I have had success without running for the JD needle. Has anyone tried using different gas? VP makes a fuel with added oxygen called Ultimate 4. Those that have tried it have gotten up to 6% more horsepower. It might be a good solution for the folks in the higher altitudes.

Ride fast-take chances.


Ckulzer, I would also think that it does indicate a lean condition but when I raised the needle it became worse and when I lowered the needle by putting the clip on the third slot from the top it was better. So my dream is to have someone out there in thumperland say to me "Oh you live at 4500 feet, well you need this size main jet and this size pilot jet and leak jet and this needle set at this clip position and your hesitation will be gone"

Here's my two cents.

1st penny, I bought the JD kit. Before JD stall on throttle snap open at idle and bog a 1/8 - 1/4 throttle. This was a real problem following my son around on his TTR90. When I was behind him and need to lighten the front end I either bogged and slowed down or, worse, bogged and then huge power surge. The power surge usually resulted in a wheely straight at the kid :awww:. The JD kit and a little personal advise from JD sloved all of the problems. Also, the bike never started easier. (carb setting is in sig for MI, below 1000 ft.).

2nd cent, I have a spreadsheet that I think I downloaded from that does exactly what you guys are asking for. You can use it one of two ways: you can start by putting in the stock MJ, PJ and needle information and the sheet will provide the theretical setting for temp and atitude, or if you have a set-up that works you can fiddle with the "stock" MJ, PJ and needle setting until they match and then you have a slightly better theretical settings. If you can't find the speadsheet I have a copy on my home computer and I can send it to anyone that whats it. :thumbsup:

Yes I would like to see the spread sheet, I don't know if you can pm that if not my Email is Thank for the help.

Check your netzero account!

Can I get a copy of the spreadsheet? Sounds like some valuable info. Heres is my email.


Do you mean check my Net Zero account because there is a problem or because you sent the info? If you sent it I didn't get it. But I did get an Email from JD Jetting who is confident he can cure the problems, I'll keep you posted.

Yamaharichey, I sent the spreadsheet to your net zero eamil account. I would think that you should have it by the time of this post. If not let me know and I will try again.

Also, based on my personal experience with JD, that the way to go.

Mparrish, I'm at work now and the spreadsheet in on the home computer so I will send it to you later today or tomorrow. If you don't get something soon send me a reminder.

A 160 main seems too small for 4500ft. :awww:

I ride 6000ft+ everytime I ride and I have a 165 main.

No hesitation, just get up and whoa. :thumbsup:

I have the JD Kit and once I set up to JD's instructions it was just a matter of dialing in the fuel screw.

160 main is just fine for 1000 feet above 80 degrees and should work at 4500 feet down to 60 degrees. :thumbsup:

The WR 450's have an Air Cut Valve that is supposed to enrichen the fuel circuit during hard deceleration. Mine has a slight stutter when just cruising at a slightly open throttle position with the J.D. kit installed. I have been told by J.D. that because of the ACV the carburation gets a little confused at those slightly open cruising positons so that the stutter you are getting is from the ACV opening and closing slightly making it go from a lean to rich condition. You may try to disable the ACV and see if this cures it. I have just learned to live with it.

About the leak jet. I feel my jetting is close to perfect but am always looking for better. Have you guys that have changed yours noticed much improvement? And where are you getting them from. Hopefully online because I hate ordering from my dealer.


I too had a stutter at part throttle cruise. At sea level it was a stutter, at 7 to 9000 ft it was a miss. I tried several needles, and pilots, with no fix. I removed the spring from the air cut and it was better, but still there. Then I pulled the gray wire and now it is just a flutter, not a miss. I think it is an ignition timing issue and no amount of jetting will cure it. But I think you can get it to a point were it isnt a pain in the a$$.

Well I got the JD jetting kit, and Im still having trouble. JD recommended for my 4500 ft. a 165 main 42 pilot red #5, that setup helped the 1/4 throttle hesitation but not the bog off idle. So he next recommended the blue at #3, that almost eliminated the bog, but the steady throttle hesitation was worse, so I tried the blue at #2, then the red at #4, the bog is a lot better but that hesitation at a steady throttle is still there, the best for that was the red at # 5. Some of you have said yours is totally gone, oh how I long to be able to say that. As you can see I have gotinto my carb at least 6 or 7 times, I like working on my bike but this is getting ridiculous

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