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Needle taper effects on fueling/AFR graph? Help.

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Hey All,

I have a question about needle taper and how it affects fueling? 
2003 DRZ400S (E model FCR39, 3x3, E Header with fiber wrap, Stock S muffler with endcap mod, and stock S cams).

JD JEtting stage 2 Kit for DRZ E model, not for the S model with FCR

Current Carb Settings:

-155 main

-Blue needle 2nd clip from top (DRZ E taper profile)

-Coast enrichener removed

-everything else stock E Carb settings (including slow jets, and air jets)

-idle screw = 2 1/8 turns out (and idles perfect)

I ordered the EMN needle as per suggestions from other TTers

My Question:  I was just wondering what the EMN needle would do to my AFR graph? The taper chart doesn't make sense to me. If you see the attached image, my AFR seems to be rich at 1/4 and 4/4. I believe the EMN needle will flatten/richen out my mid range. So, to compensate I also bought  a 150 main. Is this a correct assumption?

PS. Is the first rich state the AP effects? I know it's too rich because it's not a punchy as a pumper should be.  I'm saving up for a leak jet kit/power bowl/AP cover, but was just wonder what effects to look for when I start tuning more in the next few months as funds become available?

Thanks!

Note: Blue is first run with needle clip in 4th from top. Red is 5th run with needle 2nd from top to lean it out.

Note: dynorunShare_0.thumb.JPEG.8eee486ca5a318e322ef72977dae441a.JPEG

photo_keihin_needle_N427_oc.jpg

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IMO looks like you're running too rich on the pilot and main, you need to do some runs at partial throttle to confirm but seems to me like you need to go down on the main and pilot and richen the needle so that you don't lean out the mid end as you lean out the top and bottom. So I agree except you may have to even go to a 145 as you richen the needle.

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Granted, you need to be careful. If you run lean and mean at the top you need to keep up on the bike . A slightly clogged main and you're going to start getting close to the danger zone.

 

IMO jetting you have now looks to have a certain safety net to it except for the bottom which just looks like you have a bit too much fuel coming in which might just be to ease the drivabilty when cold.

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Thanks Swes! I keep staring at the needle chart... just as  I think I understand it..... I lose it, and I'm confused again.  Thanks for the warnings. I'm deathly afraid to burn her up, so I might just wait until dyno day again to put in the new needle and main jet. 

So what exactly is the EMN needle changing? I'm so confused. THis is how I'm reading the chart.

EMN :

  Richer     |    Leaner    |     same 

1/8 - 1/4   |   1/4 - 3/4  |   3/4 - 4/4 

 

EFT :

  Leaner     |    Richer    |     same 

1/8 - 1/4   |   1/4 - 3/4  |   3/4 - 4/4

 

Which is why this is confusing. EMN is not what I want out of a needle. I wanted a richer mid, and leaner low. Should I get another needle? Like the EFT?

 

Thanks again.

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Leaner needle on small throttle opening is a EMP or EMR. Low speed (partial throttle) is the needle straight diameter.

Realize when you twist the grip on a dyno, you get a shot of fuel from the AP, meaning initial A/F numbers are worthless unless you disable the AP and do a slow roll on, which on a Dyno Jet Roller dyno, negates its ability to measure (calculate actually) power. All your numbers show me is that might be a little rich on the main and fuel screw. The only way to test all throttle positions is with a brake dyno or with on board data logging and a long hill you can ride up in a 100% controlled method and do steady state runs

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Thanks William! So I gather all this is pointless for a few reasons. 1. I don't have an accurate A/F at 1/4  2. No Keihin needles correspond to JD red and blue profiles.  3. I probably won't be able to get accurate readings. haha

So if you had to guess, would you also say the AP is a little rich too? Should I go for a shorter duration? She doesn't feel as punchy as my buddy's DR350 with a pumper.

Thanks for the heads up. I guess I'll just install the 150 main and EMN needle I have, and take her to the dyno, and see if she moves into danger territory...if not,  then call it a win?

 

Thanks!

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1 hour ago, Funbags said:

Thanks William! So I gather all this is pointless for a few reasons. 1. I don't have an accurate A/F at 1/4  2. No Keihin needles correspond to JD red and blue profiles.  3. I probably won't be able to get accurate readings. haha

So if you had to guess, would you also say the AP is a little rich too? Should I go for a shorter duration? She doesn't feel as punchy as my buddy's DR350 with a pumper.

Thanks for the heads up. I guess I'll just install the 150 main and EMN needle I have, and take her to the dyno, and see if she moves into danger territory...if not,  then call it a win?

 

Thanks!

Unfortunately, you are pretty much right. Jetting DRZ's have been done to death. I have used a brake dyno and I also have on board data logging capability on most of my bikes. What I confirmed was the recommended jetting was pretty much 'on the money' unless you are going to chase the tail and modify jetting for any change in air density, as you might on a road racing track. Power improvements from good to perfect jetting are maybe 1/4 HP. I'd rather ride them spend all day looking for that perfect jetting setup, only to have it get less humid, a little hotter and have a weather front move through, ruining perfection. I've done 100's of runs with a DRZ 470 and only had a change worth dealing with between 40 degree winter days and 90 degree summer ones. The rest of the time, it simply did not make much of a difference to worry about.

As far as the AP, you cannot read the A/F of it, it is a crude dumping of fuel. So what you do instead is simply look for good performance. A 400cc engine or larger pretty much needs all of the squirt. You can try longer or shorter rivets on the diaphragm (that limits total volume) and you can seem if fine adjustment of the timing makes a difference (though on an E, it is a pain to do-there is a stick the Yamaha WR450 forum that covers the AP bog, the second half covers your slant style carb)

The JD needle is a triple taper compared to a EMN, so it 'might' work better, it might not make any difference at all. The plus is, you can set the jetting so lean and it will not run and you will not 'break' anything. So if it interests you, experiment. I tried a EMQ needle once, as I felt rich just off of idle. Nope. Bike would fall flat on its' face. I found the EMP was great on 90 degree days, the EMN a better winter needle. I never measured but I bet the JD ones fall in this range.

I'd probably run a 152 main. A little rich at WOT is fine for anything other than a dragster.

 

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