Near Jetting Perfection.......

Help Please.

I had YZ timing, airbox lid off, E-Series pipe w/ 9 disc, 178 main, 45 pilot, stock WR needle fourth clip, air screw 2 turns out.

It pulled like a tractor from luging to about midrange of powerband (I loved the lowend grunt!), then lopped of. And the top end was dissipointing.


I rejetted to 180 main, 48 pilot, YZ jet needle DVR fourth clip, and de-octopussed to Clark's specs (pilot air jet #100 & #65 startjet)

Now it RIPS from the midrange to Big top. More like a 2-stroke. BUT, from low to mid it doesn't pull that great. Not like it use to by a long shot. AND. if i open the throttle really quick from idle, it dies?!?!

I've tried the air screw 2 turns out to 3 & 1/4 out. It pulls a bit stronger with it 3 & 1/4 turns out, but still dies if I open the throttle really quick from idle.

Any suggestions??!?!?

I want to keep this new mid to top end monster, and I want the low end monster back.

I appreicate the help, as my wife is going to KILL me if I don't stop "tinkering" with my bike. But it's just not possibal!


i think it possible that w the yz needle your using you will need the yz pilot air jet. #75

I forgot to mention that I de-octopussed today to Clark's spes. (#100 pilot air jet & #65 start jet)


The DTM needle is way richer along the straight section at low throttle(2.715mm) than the DVR (2.755mm). The DVR is machined one clip leaner in the midrange. So, go back to the WR needle and go one clip leaner to keep the low end and the midrange.

Good Luck

Oops, I forgot to check, were you using a DTM needle to start with? The needle codes are extremely important here...

Thanks James.

I've been getting conflicting reports re: WR or YZ needle being richer/leaner. You said, along with Clark's posts that the YZ is way leaner. I've spoke to a Mechanic @ Yamaha of Beaumont who said the WR needle is leaner bacause with the throttle stop, the bike does not get as much fule as the YZ, thus leaner needle. Also, I spoke with a guy at Baja Designs who works with the Yamaha race team, and he also said the YZ is a richer needle.

Now I'm throughly confused????

What is the diffrence between the 48 and 45 pilot jet? both the YZ & WR come stock with the 45, yet it seems everyone is running the 48? Could this have to do with the quick throttle opening dying, its too rich from bigger pilot??

Thanks all for your help.


Per Clark. You need to use the DVP needle the YZ needle is too LEAN.

I,ve been working on the jetting on my bike and am getting very close. I suggest you use the search engine with reference to "jetting" and see what's up.

You may also see my post on jetting. Search under "Bill in NC".

Pilot jet 48 is richer than 45.


The first letter denotes taper D= 3/4 degrees. Taper E= 1 degree of taper.

The second letter on the needle code denotes clip height - P,R,T,V - incrementally one clip each from rich to lean. Thus, DVP#3 equals DTP#2 exactly accross the range.

The third letter denotes straight diameter - L,M,N,P,Q,R,S - increments of .01mm from rich to lean. (2.705mm-2.765mm) This will only effect 0-1/8 throttle.

Watch out for people generalizing rich needle or lean needle. They are either ignorant or don't want to take the time to help.

Good Luck

James Dean - The Needle Dr.

Dr Needle,

You da man!! This is the exact info I was looking for. I'm sitting here now with a blade micrometer and an assortment of needles and the codes all make sense to me now. So based on this info, am I correct that my stock '00 WR needle (DRS) is nearly identical to the DVR needle, except two clip positions richer and slightly leaner on the straight portion? Is running the DRS at clip 4 like running the DVR at clip 6 only slightly leaner at small throttle openings (which you could compensate for with the pilot screw or pilot jet)? I was suprised to see this because I assumed the DRS needle would be almost the same as the DTM, but it is actually much leaner on the straight portion. Do you ride a WR? If so, what needle do you run? Thanks for the info.



You got it all precisely on the mark!

Give yourself a pat on the back and go roost!

I have 2 freinds with WR's and am considering one seriously. I think Yamaha should just give me one so I could save all the greif of their customers. I've been collecting needle data for 20 years and modify needles just for the adrenalin rush of more power. It's well worth the time to get peak performance and no compromises.

James Dean

James Dean? I thought you died in a car crash many years ago? :)



Do you give needle classes? Sign me up!


[This message has been edited by Bryan (edited 04-09-2000).]


So using your formula, thru clip postion could you make the DVR basically the same as the DVP?? What would the clip position be and how did you formulate?

I am new to jetting, so please excuse my ignorance. The light is almost On.....

If I am running DVR @ fourh clip from top, and the DVR is a lean needle, and my bike dies when I open the throttle quickly, would I Lower the clip position to make it richer?

Thanks again.


All measurments I have made on various needles confirms what James is saying. I got there through a lot of measurments of various needles and a friendy Yamaha dealer. Oh ya a lot of seat of the pants testing. Kinda cool we both arrive at the same information. On this bike the needle and needle set up are critical.



DVR will not equal DVP no matter what the clip position is when at low throttle positions. The difference will always exist at 0-1/8 throttle opening. This is the straight section on the needle. DVR is 2.755mm whereas DVP is 2.735mm and will be richer. The second letter "V" denotes clip height, in which case they are identical beyond 1/8 throttle.

James Dean - The Needle Dr.

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