Jetting what else

5 replies to this topic
  • Clark_Mason

Posted May 06, 2000 - 08:52 PM


I just spend two days comparing the DVP and the DVR needles in my YZ timed 99 WR and still reach the same conclusion I reach a year ago. The DVP needle works better in my bike period. I ran the DVR in the #5 from the top with a 182MJ, 48PJ, 1.25 turns out on the fuel screw for a day and about 80 miles. The next day I ran the DVP needle in the #4 position from the top, no other changes. I ran the same route on both days with altitlude variations from 1200 to 3600 ft. The DVR needle would surge just off idle (between 0-1/8 throttle) while street crusing the DVP needle did this to a much lesser extent. The DVP needle had much improved throttle resopnse, was much snapper and a joy to ride with, like that front wheel in the air.

I'm convinced that the slightly richer DVP needle is the way to go in my WR with the YZ timing. Nothing new since I'v recommended this neeldle for the past year. However, the past two days of testing really reinforce the tremendowus benefits of the DVP needle set up on this bike. Must admit taking two days off to do a little objective testing with only one variable and a couple of nice dual sport rides was ok with me.

Just a little more insight


  • James_Dean

Posted May 06, 2000 - 09:14 PM


Thanks for the feedback Clark, DVP sounds like the needle Yamaha should have used in the first place.
James Dean

  • Dougie

Posted May 07, 2000 - 02:53 AM


So would you be recommending the DVP also to us air suckers up here in the 6000 to 9000 foot range? I still have the DVR in cause I was to lazy to order the DVP but we are in the clouds here in Denver.

Dougie, '99 WR400
Mods: YZ timing, Race Tech Suspension, FMF PC IV, FMF Hi FLo Moto, YZ seat, IMS 3.3 tank, One Industries Graphics, Renthal bars, 14/52 gearing.

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  • Clark_Mason

Posted May 07, 2000 - 08:28 AM



You high altitude dudes are probably just fine with the DVR needle. Although I'v run my DVP needle in the number 4 position from 1200 to 8500ft with no problem. At the higher altitudes above 4000 I went to a 45 PJ 1.75 turns out and a 178 main jet but left the needle a DVP #4 I worked excellent. You may want to try it.


  • Bryan

Posted May 07, 2000 - 08:56 AM


Thanks Clark.
I have used both the DVR and DVP needle here in Colorado at a ride that tops out at about 9000 feet. I agree that the DVP doesn't surge as much and I liked that.
However, I'm now running the DVR again because I'm a little nervous running the DVP with the 48 pilot at high altitude. When I ran the DVP I was running at the second clip position. I know this is too lean but I was being very conservative to avoid downhill plug fouling problems like I've had in the past. I know the DVP makes my 48 pilot act like a 50 pilot and that's what makes me nervous.
I might try and run the DVP in the 3rd position and just see what happens because the surging on the DVR is starting to annoy me. If I have troubles, I guess I could go to a 45 pilot with the DVP.

  • James_Dean

Posted May 07, 2000 - 09:12 PM


A few tidbits to use as a perspective -
( I am an engineer and always try to quantify things)
The taper of the D-- needles is .75 degrees and is calculated by using Tan(.75), this gives a taper of .013mm per 1mm length. Each clip position is .9mm. Therefore each clip position is .9 X .013 = .012mm change in needle size when the tapered part of the needle is primarily controlling fuel. The straight section of the needle changes by .020mm going from DVR to DVP.
In perspective of these dimensions the low end (0-1/8) change (DVR to DVP) would seem to be a more noticeable change than a single clip position. There is also an option to split the change down to .010mm with a DVQ needle (2.745mm diameter). Balancing the pilot with the needle straight diameter is a challenge, evaluating all the subtle varied conditions. Keep us posted Bryan....
James Dean


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