more snap & 3/4 throttle response



28 replies to this topic
  • James_Dean

Posted March 21, 2001 - 07:32 AM

#21

Taffy,

Its like chess as you said, keep thinking several moves ahead.

The only part of the needle having an affect near WOT is the taper. This is mostly with low degree tapers (D) and needing a bigger main to compensate. The #230 MAJ leaned the full throttle and maybe atomizes better as the revs go up. What about 3/4 throttle? The needle taper and MJ share it here. We're bigger on the main, now consider taper too.

Step back and look at 2-strokes. They're running 1.5-1.75 degree tapers mostly and without a pump. A single taper of 1.25 is positively dull on these and yet that is still more than "E--" needles are (1.0). The 2-stroke power goes flat in the midrange with a 1.25 needle taper. Leads one to consider F-- & G-- needles (1.25-1.5) in the FCR carb.

Getting the taper to start near EKP and DVP while keeping the #4 clip, which you mentioned and I agree, doesn't leave many choices. Look in the option charts and there are FHP, FHN, and GFP at close to #5 or FBP#2. These aren't stocked normally at Sudco, so we're exploring uncharted waters one would suspect. The FMP#7 is a Mr Hyde personality in the WR. The once friendly bike seems to be growing hair and getting mean. A more narrow focused attitude. Half throttle is getting fuel more like your test w/EKP#7, novices need not apply for this one. Muddy, sludgy conditions will require good wrist control or it's going to be screaming like a 2-stroke on the pipe. The accel pump probably needs reduced flow and the PAJ pays dividends at small throttle openings. On the other side, when traction is good the fun factor is going up again. Thats where I jump on this train. :)

Before making a global endorsement here, there needs to be more time running with it to be sure that certain conditions don't become a problem. The accel pump stroke, differing exhausts, etc. are going to have some influence on this between bikes. The temp here is 45F which works well with richer jetting. More trials will follow as time allows.

James

[This message has been edited by James Dean (edited 03-22-2001).]

  • mcarp

Posted March 26, 2001 - 07:41 PM

#22

Taffy/James-

First, a big thanks :) Just when I thought my jetting felt great, you've all given me some food for thought.

I'm always looking for ways to improve the response of the WR. James, I know we have almost the exact same bike (i have a tapered WB header, but everything else is the same). You have my last post and settings, nothings changed. My AP is not modified, though.

Guys I am MORE THAN HAPPY to do some experimenting and try to report on results. Admittedly I'm a moron compared to you guys on the carb, but I can throw in some jets and experiment over the year to give feedback, at least in my part of the world and riding style (Ohio).

Just tell me what jets to buy (part numbers :D, combinations to experiment with, etc. Since MOST of us aren't going to custom grind our tapers :D, I'll stick with OEM needles!

I'll make a nice jetting chart in Excel to record settings, environment, and observations. In fact, I'll share that with you guys over the next week via email for you to take a looksie at.

Mike O from the YZ side has offered a jetting spreadsheet, and I asked him to email it, but I haven't seen it :D

  • James_Dean

Posted March 26, 2001 - 09:04 PM

#23

mcarp,

I don't need to look your jetting up, its already in my notebook!

Your temperature and altitude are right in there to try needle FJP or FJN. This will be an optional needle for the '01YZ426. See if you can get one from Yamaha and run it in clip #5 using a #168 main without the main air jet (#200 removed). (Otherwise try FHP#4-5? from Sudco 1-800-998-3529)Don't drill the passage behind if you haven't yet.

Leave everything else as-is for a back to back impression vs EKP.

Secondly get a pilot airscrew and spring from Sudco.(P/N-021-230 & 021-235) Try it with a #48 or #50 pilot jet and air screw at about 1 1/2 turns out and see what pilot screw settings work.

If you are willing, this would be great! :)

James

  • mcarp

Posted March 26, 2001 - 10:38 PM

#24

James-

Will do. I tried a 50 once before and it ran terribly in cold weather, so I'll definitely start with the 48. I have no starting problems hot or cold (just hotstart after human error stalls) and the transition from off idle is smooth, predictable, and powerful. As you mentioned for woods/slippery stuff that's a GOOD thing.

I want it to be tamer in the low throttle opening for that reason. I love the instant transition from chug to scream when you really mean it--1/2 thottle. The EKN #4 seemed to scream too fast and made the thottle a little more delicate than the EKP #4, a reason I stuck with the EKP.

What should I expect? Will the wet spring mud have me wishing for a smoother setup?

Should I just try it on a dry MX track first?

I haven't drilled anything on the carb. Nor do I intend to! I'll let you and Taffy experiment with drill bits and $800 carbs! :)

Thanks again for all your help. I'll post back in a few weeks after trying the first setup you proposed. Will also let a YZ426 expert rider give it a test too.

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  • Taffy

Posted March 27, 2001 - 12:01 AM

#25

mcarp

i once saw that clark ran a 50 PJ. obody else, or so i thought , had EVER had any success.

today i read two posts & two of you are toying with the 50 PJ.

(shouting) IT WILL ONLY WORK IF YOU TAKE MY SETTINGS AS A COMPLETE COMBINATION.

50 PJ
PAJ Screw out 2 1/4 turns.
EKP clip 7
APJ off

Taffy

  • Taffy

Posted March 27, 2001 - 12:01 AM

#26

mcarp

i once saw that clark ran a 50 PJ. obody else, or so i thought , had EVER had any success.

today i read two posts & two of you are toying with the 50 PJ.

(shouting) IT WILL ONLY WORK IF YOU TAKE MY SETTINGS AS A COMPLETE COMBINATION.

50 PJ
PAJ Screw out 2 1/4 turns.
EKP clip 7
APJ off

Taffy

  • mcarp

Posted March 27, 2001 - 06:15 AM

#27

Taffy-

Thanks, I'll try both :)

Mike C

  • James_Dean

Posted March 27, 2001 - 07:57 AM

#28

Taffy,

With the air screw at 2 1/4 and a #48, the pilot screw was at 1 2/3.

With air screw 2 1/4 and a #50; Will this be about 1/2-3/4 on the pilot screw?.... (as an estimate mcarp)

James

  • Taffy

Posted March 27, 2001 - 08:38 AM

#29

don't know & don't ....

i'm not sure JD. i must be lucky every time i get on it!

Taffy




 
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