James Dean Carb Kit Installed ~ I Need A Little Fine Tuning

95 replies to this topic
  • Mike_Hudson

Posted July 16, 2003 - 03:36 AM


I put the 48 pilot back in last night, will be riding Friday afternoon. Should be another perfect day, 93 F and 80% RH :). Once I dial this in I'm going to put in the GYT-R baffle and see how that goes. Any thoughts on changes required? Do you think I can just change the MJ or will I need to drop the needle? I'll post results over the weekend.

  • Indy_WR450

Posted July 16, 2003 - 07:00 AM


Hey Mike,
You may have to go down to 165 or 160 main with that baffle. Everything else should stay the same. the baffle is rated at 92 db and you can shorten the tubes slightly to get more flow and closer to 96 db. Someone on this forum has done it. I forgot who and what length they cut it down to. :)

  • Rich_in_Orlando

Posted July 16, 2003 - 09:58 AM


When I installed the GYT-R buttplug on my '99, I went one whole needle leaner, DTM to a DTN. A little adjustment on the fuel screw and I was good to go. I didn't touch anything else.

  • gloft

Posted July 16, 2003 - 10:04 AM


I'm at 1500' and it's been in the high 80's with high humidity for my testing. See my signature for mods since I don't think you can make an accurate comparison without having a similar setup - especially with regard to exhaust systems. Bike really rips with snap wheelies easy in gears 1-3. I seem to hit the rev limiter much quicker now. After numerous tests, think I've settled on following jetting:

- 165 main
- Red needle, clip # 4
- 48 pilot

Hey Indy, I have 2 questions for you:

1. Did you buy the entire exhaust system or just the mid pipe and muffler?
2. Are you saying you set your idle via the mixture screw by leaning out the pilot circuit enough to increase engine RPM's . I've noticed that if I raise idle enough, I effectively eliminate the off-idle bog problems I've been experiencing. However, I've been adjusting via the idle screw not with the fuel mixture screw. Am I understanding you correctly?


  • James_Dean

Posted July 16, 2003 - 10:05 AM



The kit will also work on the Canadion model WR450. Depending on what PJ and PAJ you are currently running, the needles will cover the needed range. There are 2 settings for elevations 3-6000ft and 6000-9000ft. I would suggest keeping the stock PJ/PAJ and running the 3-6000ft recommendation. If it feels rich or lean, the lower altitude setting will be richer and the upper altitude setting will be leaner.


  • Indy_WR450

Posted July 16, 2003 - 04:51 PM


Hey Gloft,
I bought the Thunder Alley muffler which uses the stock header and there is no mid pipe. The neat thing about the ceramic coating is the pipe stays very hot and I had to put heat shield tape and insulating washers to prevent the heat from getting through the sub frame or melting the rear plastic panel. The Krizman spark arrestor (USFS approved) is like a propellar inside the expansion cone. No wire mesh. The hot gases increase flow velocity and that is why it pops like crazy down low when I switched from the stock pipe with the baha baffle. I end up needing a rich needle diameter jetting to make it pull hard. I cant get over how it pulls hard in third from idle. I can ride the woods fast in third gear most of the time.
As for the pilot, I set my idle as rich as possible without wanting to stall using the zip-ty air screw. I do not want to have to high an idle with the idle adjustment. I try to set the idle adjustment to 6mph in first gear with no throttle on flat ground. Then I adjust the Zip ty screw as rich as possible without stalling the engine at that speed. I find the bike has the best bottom end pull which is where I ride most of the time. I short shift and rarely rev the engine high. It has plenty of power down low to ride fast. :)

  • gloft

Posted July 17, 2003 - 02:53 AM



Good info . . thanks. I'm going to try your idle setup. Beginning to think I've been running my idle a bit too low which may be part of my problem. I'll post results soon.

Greg :)

  • drzphatkid

Posted July 17, 2003 - 05:45 AM


Hay wr450 you do know the zip-ty screw is called a fuel screw,not an airscrew.One more thing do you need to change the PAJ with the kit. :)

  • James_Dean

Posted July 17, 2003 - 11:52 AM


You do not need to change the pilot jet or the pilot air jet(PAJ) with the kit. Switching these jets is more fine tuning than most riders will need.
Adjusting the fuel screw is all that is needed in most cases and the needle diameter and clip position will adjust the low speed jetting for different altitudes and temperatures.

  • davidmoeller

Posted July 17, 2003 - 03:01 PM


it's seems my 450wr runs good but i worry i'm too lean carb. jetting is stock but have air box mod. grey wire, thottle stop cut, no baffle in muffler. live in milwaukee and at about 500 ft. Am i looking for burned vavles?

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  • James_Dean

Posted July 18, 2003 - 05:12 PM


You will not burn the valves with stock jetting. Yamaha has set it lean, but not enough to cause serious problems.

  • Indy_WR450

Posted July 19, 2003 - 09:47 AM


Riding in Colorado today at 9,000 feet. 48Pilot, 70PAJ, 1.25 turns, JD red clip #5, 155 main. Bike is doing very well at this altitude, 80 degrees & no humidity. JD is right you do not need to mess with the pilot circuit. I was prepared to change to a 45 or 42 but it idles the same at 700 feet. I did not change the pilot circuit at all! I changed from the 165 main, and JD blue Clip#5 and the bike runs very well for the altitude. Bottom end still pulls very well but not as strong as at 700 feet. Just a note for you guys that occasionally ride in different conditions. JD's instructions are simple and work very well. I think he could have stated that the stock 155 main is a good option at high altidude or high humidity/heat. :)

  • AkRider

Posted July 19, 2003 - 09:03 PM


Just got the kit today. I installed it tonight along with a zip-ty fuel screw. I can't belive the difference. This is the first jetting I have done on my bike. I was a little afraid to mess with it but it was easy. Anyone that is intimated by the jetting should not be. It only took me about a half hour. I only got to ride up and down the street but it rips. I'll give it a full test tomarrow.
THANKS J.D. and Indy :) :D

  • BlueThunder

Posted July 19, 2003 - 09:39 PM


My kit is installed and working fantastic.....pulls hard in all gears from idle to rev-limiter. Settings are as follows....42pj(75paj), JD blue@#4,170mj(200maj) and fuel screw@1.5 turns out(instructions stated to start @1.75 out and adjust to smooth idle). My bike has never ran so well since I bought it :D. Thanks JD :).

  • Mike_Hudson

Posted July 20, 2003 - 04:51 PM


Results of continued testing...I couldn't really tell much difference riding with the 48 PJ vs. the 45 PJ. However, when the bike was hot it would fire up w/in 2 sec using the 45 PJ. With the 48 PJ it spins for 8 to 10 sec before starting. I had the fuel screw at about 3/4 w/ the 48 and 2 1/4 w/ the 45. So for now I'm staying with the 45.

On to the GYTR insert. Went 45PJ and down to 165 MJ. MJ was very close maybe a little rich. Overall I was disappointed in the performance. The hit on the bottom end was gone, very soft. No stumbling but I suppose it could still be rich. Once the revs built top end was OK. Engine braking was much more dramatic as well although I could get used to it and adjust. So for now I'm going back to the uncorked stock pipe and the jetting shown below until I get a quiet performance pipe.

Now if only I could learn to ride :)

  • AkRider

Posted July 21, 2003 - 07:05 PM


I rode yesterday with the kit installed and my bike ran better then ever. I do have one question? What exactly is the rev limiter? I found that in first and second if I was real hard on the throttle it would cut out. I read that some of you felt like you hit the rev limiter quicker with this jetting. Do I just need to shift through 1st and 2nd quicker if I am racing through the gears? :)

  • Mike_Hudson

Posted July 22, 2003 - 02:13 AM


The rev limiter (ie revolutions limiter) is part of the electronics that limits the maximum rpm that the engine can turn to keep you from exceeding the design rpm and grenading your engine. It does feel like a miss or studdering at max rpm. You should just shift up to the next gear before you feel the "miss". I should say that the engine should be pulling hard and cleanly, w/no studdering, up to the limiter. If the miss is occuring before the engine is really wound up your main jet is probably a little rich. You can get a feel for this by changing your main jet richer then leaner and make short runs up through the gears. This is what I did to make sure I had the best main jet. Good luck. :)

  • Indy_WR450

Posted July 22, 2003 - 12:05 PM


Hey Mike,
sorry to hear the baffle did not work out. When we hook up and ride in the Daniel Boone forest you can try my bike and see what you think of the Thunder Alley pipe at 96db. We all have to get to 96db eventually. I think the performance is better than the uncorked stock pipe. :)

  • AkRider

Posted July 22, 2003 - 07:44 PM


Thanks Mike. That is what I thought. It pulls real hard right up to the limiter. I just think I get there faster with this jetting. Before it sputtered of the bottom and never realy took off like it dose now. I just wish I knew how to ride it to it's full potential :)

  • AkRider

Posted July 27, 2003 - 04:39 PM


I just wanted to keep this post going. Doese any one know what flipping the ACV would do with the JD kit? :)
I read about it on another post and it was the 1st I had heard about the mod. The post never really explained what the mod did :D Thanks for any info.


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