YZ426 Jetting Boosts YZ/WR400 Midrange Power



41 replies to this topic
  • James_Dean

Posted October 03, 2000 - 06:21 PM

#21

mcarp,
I need to qualify my position. This needle suggestion is only for those who are willing to do a little experimenting to get it right. I am still convinced that the 1 degree "E" taper needles give better snap to the throttle. The front lifts faster and less throttle is needed. This can be good and bad depending on your riding level, style, and desires.

The #100 pilot air was chosen over the #75 after going back and forth twice. The bigger pilot jet #48 just feels like it pulls better with the #100. Hardly stalls at all with this combination. :)

It is tempting to suggest that those using DVR and DRS should try EKQ or EKP first. Those using DTM might make the change easier with EKN. Each of these will work but it depends on how particular you are which will be best.

James

  • Tim_in_WA

Posted October 03, 2000 - 11:56 PM

#22

James,
I hope I'm not beating a dead horse here, but with regards to your last post, what needle would you suggest as a starting point for those of us with 2000 model EURO/CAN WR's that came with the DRQ at #4. If I remember right, I think the needle is the only difference between the EURO and US bikes. If there are other differences that you are aware of, I would sure appreciate you enlightening me. Should I just go with the DVP or EKP like you and Clark have previously suggested?

Based on information that you two have provided, I'm currently running a 172MJ, 48PJ, and 1.5 turns on the fuel screw. Currently it seems a little rich now that the riding temps. have dropped into the 40's and 50's here in the Northwest. I'm running WR timing, stock exhaust with a Vortip, airbox lid removed, no throttle restrictor, and ride 500' to 6500' in elevation. I have not done anything with the air jet, but it sounds like you suggest changing this as well. And if it helps alleviate the hestitaion like you mentioned, I'm more than ready to make the switch. Any suggestions are greatly appreciated!

Tim

  • James_Dean

Posted October 04, 2000 - 06:37 AM

#23

Tim,
It looks like the DRQ is the only difference in jetting between the US and CAN models. A DVP needle is nearly the same as DRQ but 2 clips richer. Your DRQ#4 is close to DVP#6. There will be no big change in swapping these.

The cooler temps should be leaning out your jetting not richening.

With your exhaust, cool temperature, and #48 pilot @ 1 turn, my choice would be EKN#3 or EKP#3 (same as brass needles -EMN#4 or EMP#4).

James

  • Gary_Kessler

Posted October 04, 2000 - 06:38 AM

#24

James,
More jetting joys. . .here I come!!!

I'm running the following at 5,000ft. I seems to run fine, with nice plug coloring but the midrange is weak.

All YZ mods
PJ=45
MJ=175/178 (depending on my mood)
Needle=DVP#4

I have an EKR needle. Since I'm at altitude, I think the leaner needle makes sense to start with. If I was going to the EKR, would the following jetting be a good place to start?

Needle=EKR#3
MJ=172



------------------
'00 WR, YZ modified and dodgin' Roadrunners and P-dogs. .all with no damper!

  • Gary_Kessler

Posted October 04, 2000 - 11:24 AM

#25

This link has a chart that really cleared up the confusion of which throttle openings cause certain jets have control over the fuel flow.

Hope it helps. I will figure out how to post the GIF.
http://www.carbparts...g_your_carb.htm

------------------
'00 WR, YZ modified and dodgin' Roadrunners and P-dogs. .all with no damper!

  • Tim_in_WA

Posted October 04, 2000 - 12:01 PM

#26

James,
Thanks for your reply. Would you suggest changing the air jet?
Tim

  • James_Dean

Posted October 04, 2000 - 01:36 PM

#27

Gary,
At altitude the EKR#3 is a good start. The needle straight diameter is leaner so expect to richen the pilot screw to reduce a lag or otherwise go to EKR#4. I have run a #172 with no problems, a #168 may rev better. #172 feels like better torque while #168 feels like better revs. (Maybe the airbox is restricting at peak revs)

Tim,
Probably not worth the time unless you are going to YZ cam timing. The #75 pilot air jet with the #48 and WR timing worked nearly as good. The #100 air jet was changed when I went to YZ timing.

James

  • Gary_Kessler

Posted October 05, 2000 - 04:17 AM

#28

James: Sounds like a 170 is a good compromise until I figure out exactly what I want. . . . guess I'll start there.


[This message has been edited by Gary Kessler (edited 10-05-2000).]

  • Gary_Kessler

Posted October 05, 2000 - 05:50 AM

#29

This is off of Carb Warehouse Keihn Jetting page for FCR carbs - You can see all the details at the previously posted link. .

I didn't just make this up :)

http://www.photoloft...688&w=512&h=410



[This message has been edited by Gary Kessler (edited 10-05-2000).]

  • James_Dean

Posted October 05, 2000 - 06:24 AM

#30

Thanks Gary,

This posting is all about increased NEEDLE TAPER. Note the throttle opening range that the needle taper affects. The STANDARD needle taper recommended by Keihin is 1 degrees. Yamaha has been using 3/4 degrees on the 400. I am simply recommending the standard FCR needle taper to avoid lean conditions and to get better mid-throttle response. :)

James Dean

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

Posted October 05, 2000 - 06:49 AM

#31

James,

Understood about the posting thread. :D

I found the diagram helpful in understanding when and how the needle taper effected the fuel flow. And at what point the needle taper transitions to the MJ. For us folks that are "carb impaired", pictures are worth a 1000 words! :)

So, with increased taper, as the diagram indicates, then the mid-range effectivness would be even greater? Which would explain why you would need a smaller MJ to accompany the new needle jet. The light is starting to shine!!! Thanks! :D

------------------
'00 WR, YZ modified and dodgin' Roadrunners and P-dogs. .all with no damper!

  • Taffy

Posted October 05, 2000 - 02:08 PM

#32

coupla things. can we drop the use of the phrase "needle jet" & stick to "needle" only the trouble is that that brass tube your needle goes up & down in is called the er um needle jet-i call it the emulsion tube. & the needle is the jet needle-or is it the other way round o what the hell!!!

it's the NEEDLE.

the other thing is; would someone confirm that hitting the rev limiter is a misfire every 2 or 3 seconds?

Taffy

  • Clark_Mason

Posted October 05, 2000 - 04:08 PM

#33

James

Hopefully you have received my modified EMN needle and will be evaluating it soon??

Clark

  • James_Dean

Posted October 05, 2000 - 06:52 PM

#34

Clark,
Yes, I got your EMN and it is VERY close to what is in my bike right now! I will also try your jetting specs with it for a comparison to my favorite settings.

Taffy,
What gets confusing is when the manual calls the needle the jet needle and the emulsion tube is called the needle jet. Terms like needle and nozzle work for me.

James :)

  • Taffy

Posted October 05, 2000 - 11:06 PM

#35

what about the rev limiter-how does it feel when you hit it?

agree about the names JD. did you check the code of the emulsion tube when you talked of going to the E** series needle.

while i'm asking could someone who has a YZ base gaket please measure the thickness of the gasket, i hope someone has one on their shelf.

Taffy

[This message has been edited by Taffy (edited 10-06-2000).]

  • Gary_Kessler

Posted October 06, 2000 - 04:32 AM

#36

Taffy -
I THINK I've hit the rev limiter - at least that's what my yamaha part manager said when he rode my bike.

Hard to explain. The bike pulls really hard until right before WOT and then it just starts "stumbling" and won't accelerate past that point. If you lower the revs by upshifting, then it goes away until you hit that spot again. It's very consistent and jetting doesn't fix it.

I just put in a longer throttle stop (3mm), so I'm going to try it when I get my bike back together. It's REALLY annoying!!

------------------
'00 WR, YZ modified and dodgin' Roadrunners and P-dogs. .all with no damper!

  • James_Dean

Posted October 06, 2000 - 07:17 AM

#37

Taffy,
I've run up to the rev limiter many times but don't have any specific numbers on the rev limiter frequency. Thought someone else would but it feels like a higher frequency stutter. It is not like the older (-1992) Seadoo watercraft that cut out at about 1X per second and feel like a intermittent kill switch. It feels more like 5X per second as on newer models. If you want to experience it ride your bike in 1st or second on the flat and hold it wide open.

The emulsion tube codes are identical for the '00WR and '00YZ even though the WR uses DRS and the YZ uses EKR. ( and it is called a "JET, NEEDLE" not to be confused with a JET NEEDLE :) )

James

  • Gary_Kessler

Posted October 23, 2000 - 08:18 AM

#38

James,

Basics first:

PS = 2.5 turns
MJ=172
PJ=45
Needle=EKR#3
Elevation= 5000
YZ timed.

Finally put the EKR#3 needle into my WR w/MJ=172. It makes a BIG difference in the mid-range. Pulls harder and gets rid of the rollon. It adds another order of magnitude to the fun factor. I roosted my son pretty good with some good ol' New Mexico red mud!

Rejetting also got ride of the sputter on WOT, which leads me to believe I was rich on the MJ.

I think it's still a bit lean, so I might change the EKR to clip #4 after I ride it a bit more.

Excellent suggestion! Thanks!

------------------
'00 WR, YZ modified and MX-Tech suspension;now if I could just ride it.

  • rowellcory

Posted March 12, 2013 - 04:52 AM

#39

james i got ekp ekn and ekq i have a 99 wr400 with a stock needle open stock pipe 170 main 75 pilot air jet 48 pilot and i ride at sea leval to 2000ft im going to try the ekn first but was wondering if i should switch to a 100 pilot air jet thank you

  • rowellcory

Posted March 12, 2013 - 06:32 AM

#40

sorry james i said i had a 75 pilot air i think i meant main air




 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.