Results of DVP at 9,000 feet

I rode my YZ timed 99 WR the other day in the chilly mountains of New Mexico at about 9,000 feet. This was the first ride since the installation of the DVP (4th notch from the top), 48 Pilot, 178 Main.

Results were as follows: Decent mid-range, a little sluggish on top. 1/4 to 1/2 throttle a little rich.

Dropped the main to a 172 and immediate snappy improvement on top end. Very crisp...

Bottom end: 1/4 to 1/2 will rev out o.k. once...then if you let off and immediately re-apply throttle, the bike bucks and burbles then cleans out.

Looks to be a bit rich... I think I'll try to go to the third notch from the top. I'll let you guys know what I find out.

Incidentally, the the very bottom end (0 to 1/4) seems spot on, starts easily at all times, very slight popping upon deceleration downhill...1 turn out on the fuel screw.

What do you think ol' jetting gurus?? Am I headed in the right direction here? Anyone else run there DVP on the third notch at this altitude?

P.S., I think I may have to put a richer main back in too after I lean the needle back out a notch huh?

[This message has been edited by Vincent (edited 11-04-2000).]


Good inputs on your conditions and setup. The clip position is the right thing to change for the throttle range of 1/4 to 1/2. Sometimes I get this same burble rolling off and on riding gravel roads. Will be interested in how it works after your changes. Might suggest keeping the 172 main until you see what the clip does.


Ok...went riding yesterday at the same altititudes. 3rd clip from top on DVP, 48 pilot, 172 main.

Ran good all day, 1/4 to 1/2 burble completely gone but... seemed to be a little blubbery on the bottom at 1/8 to 1/4 throttle.

Sounded a bit lean so I tweaked fuel screw from 1 turn to 1 1/2 turns. Ran better all day until the trip down the mountain. Once at the truck I cracked the throttle to open it up a little and whoala... I had a semi-fouled plug, dang it!!! First time I've ever fouled one.

Is it because I went out so far on the fuel screw? Bear in mind I'm not de-octopussed, I have stock exhaust (uncorked of course), YZ timed.

I may just go back to running my DTM needle at the 2nd notch from top, with 42 pilot and 168 main...plug always ran good and tan with that combo.

What kind of performance gains am I looking for to convince me to stay with this DVP needle?

James, what are the differences in taper between the 2nd notch on DTM and the 3rd notch of the DVP??

I know the DVP is leaner across the board but is it worth the hassle??

[This message has been edited by Vincent (edited 11-12-2000).]


The DTM#2 is EXACTLY the same as DVP#3 past 1/4 throttle. The middle letter runs in 1 clip increments with letters R-T-V-X.

The last letter refers to the straight diameter. The M is 2.715mm, P is 2.735mm and is leaner. M is the richest of any choices Yamaha has used for SEA LEVEL jetting. At 9000 ft the P should be better unless it's very cold.

Are you using a #100 pilot air jet? This is a good idea with the #48 pilot jet. I have been keeping the pilot screw between 3/4 and 1 1/4 at sea level with a #100/48 combo. This makes it look like your pilot screw at 1 1/2 was too far out and fouled.

Otherwise a #45 pilot jet (2 turns out) and #75 (stock) or #100 pilot air would be my choice.


[This message has been edited by James Dean (edited 11-12-2000).]


The DTM needle is too rich for YZ timing at the altitude you are at you are much better off with a DVP or a DVR needle. At alitiudes above 7000 with YZ cam timing I usually run a DVR #4 or #5. I always run a 48 PJ and just vary the fuel screw from 1/2 at high altitude to 1.5 a sea level. I'll run the DVP from Sea level to approx 7000 and then if I will be spending any significant time above 7000 say a couple of days riding then I would go to the DVR needle.

If you want to continue using the DVP at those altitudes I would follow James Deans advice and work on the pilot jet or fuel screw.

If you had the fuel screw put at 1.5 turns and went down a long run above 7000 feet in altitude you are asking for the bike to load up and foul a plug. I would suggest 1/2 to 1.0 max on the fuel screw with the 48PJ. I feel at those altitudes the DVR is a better match for the 48PJ. (I'm just lazy as changing the PJ is harder than changing the needle).


I kind of figured thats what you were gonna tell me. Too many turns out on the fuel screw. I just left it there because it sounded better initially, just above idle.

I suppose I'll turn the fuel screw in again, put in a smaller pilot jet and give the DVP another chance.

Any idea why I cant seem to run the same jetting everyone else seems to get away with (I.E, 48 pilot, 4th notch DVP, 178 main) at more or less the same altitude? I find this puzzling...I run a clean air filter, not over oiled, yet it seems all the Colorado folks run the richer jetting with ease. Weird...

[This message has been edited by Vincent (edited 11-13-2000).]

It may be production tolerances -or- with a smaller pilot jet or less turns out on the pilot screw, you might be able to run in the 4th clip.

Are you using a #100 pilot air?

Hi James,

I am running on a 98 WZ timing WR, I am riding on sea level using DVP 4 clip ,50 pilot, main 175. What will the effect be if I used a 100 pilot air jet and using the stock start jet60. Do i need to remove the octopus by using just this combination or do I need to change both jet in order to remove the octopus. Thanks

The #100 works well with the #48 pilot in my '00 WR. The #50 was too rich for the combinations I have tried. The start jet was not affected in any noticeable way.

Clark or someone else will have to speak about the octopus effects as the '00 WR doesn't have it.


Running the 100 main start air jet along with the octopus will lean out the bike during starting and decelleration as both the 100 primary and 95 secondary air jets will be in effect (the secondary activated by the octopus).

I would recommend you ditch the octopus as it is a air leak waiting to happen as there are a lot of hose connections associated with it.

If you are going to the trouble of changing the primary start air jet from a 75 to a 100 why not remove the octopus at the same time it is a simple process just follow the instrucitons in the technical section and do not forget to block off the two ports indicated.


HI Clark and James,

It has been very long since I wanted to ditch all the octopus away. But I still can't get hold of the secondary 65 start jet. So it is ok if I just used the 100 air jet, the stock 60 start jet size and ditch away the octopus. :)

Thanks. :D


Yes its ok remember the start jet only comes into play when you use the choke. I'm sure you will be just fine. That is the way my WZ is set up.


[This message has been edited by Clark Mason (edited 11-14-2000).]

Hi Clark,

I try it out yesterday and the bike somehow was not so responsive on the low and the mid to top end hit was softer. So after messing with the fuel screw and test riding for two hours. I have gave up and I installed back the octopus. I have block the two holes and the only thing that I can suspect is the lack of the start jet 65 maybe or somehow affect the bike performance. Anyways thanks for the helps



Sorry to hear that removing the octopus did not work our for you. I must admit I do not know why as many people I know have removed theirs with excelletnt results me included.

Good luck


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