Jetting...Where do I go from here?

36 replies to this topic

Posted July 02, 2002 - 03:51 AM


The 2001 DRZ 400 uses a Kehin 39mm carb which is essentially the same as the 98/99 WR/YZ carb's. All the jets and needles are interchangable. The only difference is that the DRZ mounts the Hot Start button on the carb instead of the frame. (Which I moved to the handlebars because it was such a pain to work around.

I used to think that jetting was a foreign language until working with JD and Taffy on several different jetting projects that I was working on. The main thing is to match the correct Fuel supplying jet with the appropriate Air jet for the application. Then dialing in the needle to make everything come together. JD has a great spreadsheet for sale that takes much of the guess work out of the process. It will first appear to be written in Greek but is a pretty good document. It is a valueable jetting tool and I would recommend getting it.

The BK mod is primarially geared toward the 00 and later carbs. The KL Mod is geared for the 98/99 carbs. Personally I don't get a warm and fuzzy about drilling out a part of the carb that supplies fuel....I did that once years ago and lost a Yamaha 360 to a post crash fire because of it. Taffy has a mod as well that I will be looking strongly at. I like the P38 because of the simplicity, granted it cost's $65.00, and you still need to trim the rod some. Both Taffster and JD have a point and I'll take a look before deciding on a final solution.

Bonzai :)

  • James_Dean

Posted July 02, 2002 - 06:33 AM



See: http://www2.towerhob...ars&FVPROFIL=

These are the locking axle collars for RC (Remote Control) airplanes. The 3/32" collar just fits the 2.5mm rod that goes down to the pump. They come in a package of four for ~$1.30. The outer diameter is 6.4mm which is nearly the same as the 6mm brass tube that the rod goes into. It also comes with the tiny allen wrench to tighten it. I found it at the local hobby store.


[ July 02, 2002: Message edited by: James Dean ]


Posted July 02, 2002 - 06:44 AM


Oh Man... Your not gonna believe this...

I called Towerhobbies, The Price for the part is $1.30, and shipping is $7.99.

Thats Highway robbery......

Bonzai :)

  • Old_Novice

Posted July 02, 2002 - 06:47 AM


Thanks both of you. I already have the collar on my AP rod limiting stroke to 2mm. It did seem to be the more adjustable/cost effective option. I have the DVP needle and a 100 PAJ on order so I can continue to fine tune.

FWIW, a buddy of mine disasembled his YZ carb last night to let me know what he was running as his bike has not been touched jetting wise since he bought it.

DVR 4th position
MJ = 175
MAJ = 200
PJ = 45
PAJ = 100
SJ = 65
FS 1.75 out

Looks like I am working my way toward his jetting, though even he is questioning the 175 MJ at this altitude. He is also watching closely to see how the 42PJ and DVP needle work in my bike.

Nothing like being the lab rat.

Yamakazi, I gotthe collars at the first hobby shop I tried here in town. Apparently they are a very common item.

[ July 02, 2002: Message edited by: Old_Novice ]

[ July 02, 2002: Message edited by: Old_Novice ]


Posted July 02, 2002 - 07:27 AM


Yep, Thats stock YZ jetting....

You have not said what kind of pipe you are running on your bike.

Personally I would recommend a needle change to the OBEKN needle. I have tried numerous needles and configurations that have been recommended on this board, However the EKN above all the rest seems to provide better punch and snap than even the YZ needle in the WR. For $13.00 you cannot go wrong.

Bonzai :)

  • Old_Novice

Posted July 02, 2002 - 09:18 PM


"Yep, Thats stock YZ jetting...."
I would have thought the loccal dealer might have adjusted that for the altitude. He swapped in a 170 main today and said it was like a new bike on top.

"You have not said what kind of pipe you are running on your bike."
Complete Big Gun Exhaust (w/spark arrestor). The stock WR pipe is collecting dust in the corner right now.

Since I cannot do any more testing until the weekend I may have my friend try the 42 PJ and 168 main I picked up at lunch.

"Personally I would recommend a needle change to the OBEKN needle."
Once I get to a place where I am satisfied the bike will run OK i.e. establish a baseline, I might try one (ore more) of the Exx needles. I want to get this bike rideable and learn more about jetting this specific carb before I begin a search for any more power. The way it runs right now I would be afraid it might hicup and try to kill me on a double.

  • James_Dean

Posted July 02, 2002 - 10:12 AM


I called Towerhobbies, The Price for the part is $1.30, and shipping is $7.99.

Thats Highway robbery......

But you can buy them in bulk at $3.49 per 12 pack and get over 200 collars for the $65 price of a P-38!!


  • Hollywood

Posted July 02, 2002 - 10:30 AM


Yamakaze, Check your PM.

I also have a bag of the 3/32" wheel collars - I'm happy to mail you one.

JD, Purchased your spreadsheet yesterday (I'm in ATL and had questions regarding my DRZ) I'd like to talk with you more on interpretation of the charts.

Yamakaze, I'm very interested in your friends DRZ jetting recipe - it sounds like what I might be looking for to get ride of my midrange "mwooooog"!!!

Best Regards,
Mike (Hollywood)

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Taffy

Posted July 02, 2002 - 12:51 PM


i'm off, before laurence olivier takes up dentistry.



Posted July 02, 2002 - 01:06 PM


Now That's Comedy.......Taffy you kill me.....

Bonzai :)

  • Old_Novice

Posted July 13, 2002 - 02:21 PM


After waiting nearly 2 weeks for parts to arrive, they slowly trickled in over the past week. The women were off to a candle party and I had the whole afternoon to resume the jetting adventure uninterupted. What a dissapointment to find the WRONG needle in the package that should have held my DVP. :)

As it was, I did change to the 42 pilot and got the bike to pull (not bog) from a closed throttle, whackinng it open. Not what I would call "crisp" but it is definately getting better.

Current setting:
DVR 4th position (waiting on the DVP...again)
MJ = 165
MAJ = 200
PJ = 42
PAJ = 100
SJ = 65
FS 1.75 out
Taffy collar adjusted from ~2mm down to ~1.5mm

Mid 90s here today as well. Cold, the bike started first kick with the choke. Once the choke was off, it did not idle as smooth as it has in the past, but not bad. Re-started hot on one kick with out the hot start button after a short ride to top off the tank. Now that the hesitation is gone when grabbing a handfull of throttle I am much less afraid of taking it off road for a real ride.

  • LarryCO

Posted July 16, 2002 - 09:29 PM


I'll save you a bunch of time here...been tinkering with jetting out here in CO for a year plus now...and I'll share what works best for me...

38PJ/65PAJ/1.5 turns PS/EKP#3/150MJ/160MAJ.
WR timing, BK mod, stock uncorked exhaust.
Starter jet is still stock (65 I believe).

This setup runs extremely well at Rampart...7K - 9500 ft...and pretty darn well in town at the tracks (5500 ft). Havent quite finalized my final setup for anything over 10K. If you want more detailed info, I started a thread posting all of my results out here in Colorado and's entitled "High Altitude Jetting - CO" or something like that.

Hope this helps...


  • Old_Novice

Posted July 16, 2002 - 09:46 PM


Thanks Larry, I had thought about simply copying your set up but was not sure if the differences in the 400 vs 426 carb wold be an issue. Having recently read and re-read some of the other jetting threads, I can see I am headed in the direction of your setup now. I may go straight there from where I am at now and fine tune if necessary.

  • Taffy

Posted July 16, 2002 - 01:36 PM


old novice

the reason your tickover is a little rougher is because the dvR (emphasis on the R) is too lean on starting and idle. this is compensated for by the usual PJ's that riders run. up near 45/48.

but the PJ's are there for slow speed and that's where you must value them. the real way to get a smoother idle is to get that dvP needle.


  • Old_Novice

Posted August 02, 2002 - 03:59 AM


Time for an update. Last week I was able to get to the track for the first time with this bike (the first time in nearly a year on any bike!). I was really slow (sorry if I got in your way Murf, I read in a post the next day that you were at Aztec that afternoon too), but the WR ripped the way it was set up. PJ=42, PAJ=75, MJ=165, MAJ=200, SJ=65, DVR #4, FS 1.75 turns, AP spacer ~ .060. It pulled well throughout the rpm & throttle position ranges. When I got tired I could ride the whole track in 3rd gear it pulled so well. The only real drawback was a bit of popping on decel, but even that was not real bad.

After much waiting and parts counter confusion, the correct needles finally arrived. I had to try them so last night I had a short jetting fest.

First test: PJ=42, PAJ=75, MJ=165, MAJ=200, SJ=65, DVP #4, FS 1.75 turns, AP spacer ~ .060.

The bike ran just like it did at the track, minus the decel popping. Started fine and idled smoother than it ever has.

Second test, the LarryCo setup w/Taffy inspired APJ setting: PJ=38, PAJ=65, MJ=150, MAJ=160, SJ=65, EKP #3, FS .75 & 1 turns, AP spacer ~ .030.

This jetting changed the entire personality of this bike. Super responsive in the lower RPM & smaller throttle settings. The most responsive it has ever been when whacking the throttle open at low wheelie machine. Taffy, is this the "snap" you are referring to? Overall it seems a bit lean as it does not pull near as hard in the mid to upper RPM range (there is a noticeable buzz in the bars now too), and the decel popping has returned and is more pronounced than ever.

Next step I believe is to go back and play with main jets to try and sort through this setup from there. I want to get back the oomph that l had with the DVP setup coupled with the response I now have with the EKP. I am going to put the DVP setup in my friend's YZ so we can continue to experiment with these two setups and do side by side comparisons.

Again, THANK YOU! to all that have provided me with input, part numbers, and kept me pointed me in the right direction along the path to jetting enlightenment.

  • LarryCO

Posted August 05, 2002 - 05:39 AM


Good to hear that your jetting is coming around! Yes, admittedly that 150MJ may be a bit lean on the higher end when racing around in town...but you'll be glad that you're running it when you go to higher altitudes. Replace that 150MJ with a 155MJ and see what happens...then go up from there until it's too rich.


  • Old_Novice

Posted August 05, 2002 - 10:49 AM


LarryCo, I acutally did just that. I spent the weekend working on the Jeep and was using the WR to chase parts. Whenever I made a tirp to the parts store I would change a jet or adjustment. The 155 MJ helped, but I definately have a part throttle lean situation. Ran great if I hammered it from stop light to stop light. Good thing the parts store is close. Too much of that and I could see a ticket in my future (wheelie, shift, repeat...I really should install a speedo) :)

I think my exhaust is allowing a leaner condition with my bike than what you have. I'm not done yet, it seems I am just now starting to understand how all of this works. And if I do this correctly, I am hoping to have a jetting solution worked out for both this and higher altitudes.


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