Jetting EKP vs DVP

Servus James,

Originally posted by James Dean:

Lately I've been trying a few more modified needle combinations on a quieter exhaust setup. Haven't gotten it to my satisfaction yet.

On Saturday I was running the DVP vs. EKP needle with my special quiet-insert for my WB E-series exhaust. The "quiet-insert" is a selfmade copy of the thumper/Vortex insert for the XR 400 adapted to the WB exhaust - works really well and only takes away some midrange snap. While the EKP is working fine, it is no match for the DVP setup. The DVP works so much better on bottom and top that the boosted mid of the EKP is not really missing. That's it for me - I'm sick of the noise so I keep the insert even for MX and the DVP jetting is a much better real-world performer than the E** needles, which only shine in particular circumstances.


So Clark and James what would you recomend- Ride in So Cal elevations, have the DVP #4, 180mj, 48 pilot, 1.75 turns out on the fuel screw, and I'm happy with the performance but would certianly like some more hit or punch-

Would you reccomend the one of the stock (non-modified needles) like the EKP and another main jet or keep the trusty DVP set up?

Thanks, Harold

Latest perspectives:

The setups that best suit the EKP(EMP) needle profile appear to be less restrictive exhausts and are louder. The most difficult jetting setup that I've found is when the YZ cam timing is put with a quieter spark arrestor. The DVP may be a better needle in this case. The verdict is not in yet.

Clark has the EMN working with a small alteration. This is a smaller straight diameter(richer low end) and the increased taper of the E-- versus the D-- needles. Possibly EMM will need to be looked at for more restrictive and quieter S/A & YZ timed setups.

Suggested starting points at 0-4000ft 70F:

A)YZ or WR cam timed, free flowing exhaust (loud)- EKP#3,EMP#4 or EKN#3,EMN#4

B)YZ or WR timed, semi quiet S/A - EKN#2,EMN#3

C)YZ timed more restrictive exhaust - DVP#4 or #3 or E??

DVP covers a broad range with good off idle performance. EMN or EMP are for the increased mid-range and need smaller main jets.

I'm still tinkering :)

James Dean

As I'v stated for over the past year the DVP needle with YZ timing is an excellent all around performer and tough to beat. In So Cal between 1000 and 6000 feet I run the DVP #4, a 48PJ, fuel screw between 1.0 to 2.0 turns and a 180 or 178 MJ.

At altitudes above 6000 if I will be at that altitude for a while (couple of days, etc) I will run a DVR needle in the #4 or #5 and a 175 MJ.

As to the recent jetting experimentation using the E** needles its been a tough search and I'v setteled on a EMN needle with a slight mod to make it look like a DVP #4 between 0 to approx 1/2 throttle and then the standard EMN above that. This needle also works excellent but I still occasionlay get some odd stumble but not often. If I'm riding hard with lots of throttle operation its fine. Its when crusing that I notice the occasional and I mean very occasional stumble. I'm running EMN mod #3, 48PJ 1.5 fuel screw, 165MJ.

I'll run this for a little longer and then go back to the DVP and based on this make a final decision on what to run long term.

I concur with James Deans observations about the exhaust if you have a good flowing exhaust it will be more compatible with the "E" taper. And lastly my bike is a 420 running a 13.5 to 1 Weisco piston, its been ported and I'v run the Stroker and FMF PCIV-2 spark arrested exhausts. If I still had my WB which I sold to Bryan I bet it would be more compatible with the "E" taper yet.

One thing I noticed since I installed the 420 kit I cannot hit the rev limiter with the Vortex ignition. With the standard 400 configuration I hit it regularly. I feel Its fighting the 13.5 to 1 compression as the revs build and cannot get there. The bike rips on the bottom and mid range but on top the 400 was faster. If I went back to a loud performance exhaust probably would get a few more R's but my head would be hurting. The bike is a much better trail and dual sport mount now than before by quite a large margin--more torque, predictable slow speed operation, less stalling and pulls taller gearing easily for street crusing.


So Clark, if I run at 4,300 to 9,300 feet should I get the DVP or the DVR?

I dont mind running the clip a little higher than #4 on the DVP if I can gain the desired results.

99 WR400F, YZ timed, stock exhaust (uncorked of course).


just an idea. i tried the EKP on holiday & have just taken it out tonight as i'm racing sunday.

i also felt this all over the show hesitancy. i feel that if you were to try disconnecting your APJ & try gentle roll on throttle tests you could get the needle setting a lot closer. a lot of your needle work may be shrouded by that squirt of juice. hook up your APJ again for the zero to WOT tests.

i've also read somewhere that the point at which the APJ works has been improved for 01-worth checking out?

how about a rolling road check?


Either needle will work depending on how you set up your pilot circuit, what clip positon you run and the basic condition of your scoot. As I said run your fuel screw between 1 and 2 with the DVP and move it closer to 1 or 3/4 for the higher altitude stuff. You may want to experiment between #3 and #4 on the clip. The DVR needle is slighty leaner on the bottom but it also starts its taper a little sooner (richer) so jetting it also takes a little balancing of the pilot circuit and a slight adjustment of the main jet. We are splitting hairs here and the DVP will be fine. Remember I like to tinker so I often run both needles and make my selection depending on the altitude and air temperature one will be ever so sligtly better than the other.

For all around the DVP is a excellent choice. Use it at the altitudes you mentions and experiment with the #3, #4, fuel screw 3/4 to 2, and a 178 or 175 MJ and you will find the best combo for where you ride



Throughout this jetting experiment I have been evaluating differeint accelerator pump start points but with the E** needles I feel its the needle rapid transistion from leaner to richer thats dominating the problem. I will continue my efforts.


For what it's worth:

I have tried the EKP needle with MANY clip/pilot/main combinations and could not get it to work well. There was always a stumble or hesitation somewhere.

I finally gave up and went with the DVP and am much happier with the performance.

I'm running the stock pipe with baffle removed and stroker quiet tip on a YZ timed 99 WR.

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