Deciphering the Keihin needle code.

[Varastorm]

Help, I have been trying to decipher the Keihin needle code most of the day & I am well & truly stuck.

I have measured up the needles & have a good idea of what does what how to correct my Jetting problem.

Obviously I would rather crack the oem code & order the needles, but if I can't..

I was thinking about decreasing the DJ needle straight section diameter from 2.85mm to around 2.75mm & see what effect it has

I was going to experiment by removing the metal (slowly) from the needle with 1200 wet'n dry & hold the needle with a drill.

I don't really want to experiment/modify the DJ needles & there's no point in playing with the Std needle either as they're too short.

Any help would be brilliant, thanks in advance

[NZSpokes]

Dont know if you have looked at these,

http://www.dirtrider.net/justkdx/jetneedles.html

http://www.kyajet.de/?lang=en

[Varastorm]

I have read lots of those charts & the answer seems to be that Honda don't want us to know what needles they use. So we can correct their poor needle choice.

I thought this is a good read http://davestestsandarticles.weebly.com ... jetage.pdf

The best advice "modifying solution" seems to come from motor cross & jet ski forums. They recon that if the needle is mostly good & you can identify the troublesome (lean) throttle area, just file a very small flat (works fine and more accurate) than sanding the circumference.

I do feel the DJ needles are very good with the clip in the second groove down from the blunt end, the dyno proves it & my ass.

From what I have read, it seems that it's the straight section that is too large a diameter & making that fuel zone too lean.

So here are my choices,

1, Remove the DJ needles & with a micrometer carefully file a flat on each "straight" section of the needle, if I mess it up slightly put the biggest flat (richer needle) in the rear to aid cooling

2, Remove the DJ needles & place the groove section in a drill, then carefully apply electrical tape to the section I don't want to touch. Then use wet & dry on each needle checking constantly the diameter micrometer until you get the desired diameter.

3, Measure up the DJ needles & cross reference the dimensions to a Keihin needle so we can all have access to a needle that can eliminate any rich or lean areas for ever.

Number 3 is the one I am gunning for & this is what I think so far, please correct me if I am wrong

The needle type is N427-48, & they are all 66mm long. Std A1UC needles are 59.8mm top to bottom, so at a guess the extra length is to accommodate the grooves at the top for different clip heights 5x @ 0.9mm increments.

I also think that the "A" in A1UC designates the taper of 1°, as there seems to be only one main taper apart from the tip. Which is there for safety reasons, to stop the needle coming out the needle jet hole & jamming the slide wide open.

I also think the U in A1UC designates the diameter of the "straight" section which is 2.785mm. Which would tally with the chart from Allens performance http://www.allensperformance.co.uk/data-n427-48.html.

But my micrometer reads 2.810mm on the "straight" section, which = X or W on the Allens chart??

Then I've tried to work out the"L1" length in the Allens chart, by measuring how far the 2.515mm needle diameter was down from the under the "top hat" of the Std needle which is 19.52mm.

Then, to try & make some sense of the figures add 5 different (imaginary) clip grooves to the Std needle @ 0.9mm each = 4.5mm.

So we have 19.52mm + 4.5mm = 24.02mm. Which does not tally with any "L1" lengths, the shortest "L1" seems to be 34.55.

So then this is where my guess work ends, until I get the DJ needles out & measure them up.

[Varastorm]

Here's a good read about cutting your own needles, it's in German & about SU carbs. But gives a little more insight to the theory.

I just copied & pasted into Google translate

http://www.bobs-services.de/pdf/2003_12_nadel_de.pdf

[8541Hawk]

So we can correct their poor needle choice.

Please don't take any of this wrong but........

First Honda did not make a poor needle choice. You changed things. In stock form the VTR needles are some of the best I have ever used and I have been tuning carbs longer than some folks here have been alive.

While it is good to see folks take the time to try and figure out how to tune carbs, there is a reason carb tuning is or was considered almost a black art and not just a mechanical bit to pop a couple parts into.

Yes there is a lot of info on the 'net and folks will say that this or that is the "answer" but it is not...... each bike is different.
All the charts with this happens at a set rpm and that happens at another rpm are just "base line" numbers as it doesn't always happen at those rpms or other things are also happening.

I could go one but lets just say it took many years to actually get a good handle on what is actually going on.

To keep it short and simple, first for tuning. One of the big issues that make it tough to get these carbs completely dialed in is that you are missing 2 of the "common" tuning tools.
That is the slide cut out and the height of the fuel in the bowl.
I won't waste time to explain what they each do but yes it would help with some of the common issues but as you would have to make the parts yourself, it is not worth the time.

As for the Keihin needle code...... You will never figure it out...sorry they are very guarded with that info. Though it is understandable when you look how much Honda spent so they could have the info...... They got it by buying Keihin carbs.....Yes they are owned in full by Honda.

I have never seen them slip up in this area...... even the HRC kit listed the needle part numbers as "XXX-XX-XXXX" so it would be nothing more than a guess to try and figure out the numbers.

Again don't think I'm saying you shouldn't try to figure this stuff out, it can be very rewarding.
Just remember that carb tuning has always been a specialty for a reason and if it was just reading the charts and changing bitrs by what rpms they stuff is happening, it would be easy and everyone could and would do it.

Carry On.

[Varastorm]

First Honda did not make a poor needle choice. You changed things. In stock form the VTR needles are some of the best I have ever used and I have been tuning carbs longer than some folks here have been alive.

The reason I mentioned that the needles are poor is that even on Std VTR setups the needles are wrong, all the graphs show mainly good off pilot jetting but super rich prior to the main jet fuelling zone. There are no Std VTR dyno sheets anywhere to prove me wrong.

They're all around 13/1@3000rpm going to 10.5/1@5750rpm, some way lower than 10.5/1afr @5750rpm. That isn't a good needle.

I am sorry but that is poor in my book & it should be in yours. If you took your bike to get jetted & they gave it back to you like that would you think it was good?

The needles are too lean low down & too rich higher up the rev range, if you correct the low speed running the higher midrange is too rich & vice versa.

I think we can work out what Honda needles are, I recon I know what to do to a DJ needle to make it perfect (for my setup). We have the Std needles & we have all the charts we need on the internet.

The only thing I need is a set of aftermarket Keihin needles from Allens, then I'll work it out & pass on the info here for you to discuss

[8541Hawk]

You win...... I don't have a stack of charts lying around and I tell folks to raise the needles because I guess I'm clueless as that is making the stock needles ever shorter.

The the fact that there are 100's of folks that run my carb set up ( On the other board where I first posted my set up it has 56,719 views so far) and it works just fine for the majority of folks.
Even then, it doesn't work for every bike and I claim it to be no more than a base line as you will need to tune it in to your bike.

Now for the fat spot you talk about, yes I address that issue and IMHO it is not a needle issue. It is a slide speed issue and I take care of the rich bump with my set up without the need to find one off needles.

Another hint I will give you as a carb tuner and a machinist, the only way you can accurately measure the needles is with an Optical Comparator. It is the only way you can measure the tapers.
Also the needles are hardened (or they would wear out prematurely) so your idea of modify one with sand paper is going to be difficult at best.

In the end, like I said, it is god to see the interest in a dying art.
Believe it or not I am only trying to help you out not be negative.

Another final tip, as I am not going to argue with you,
Don't be so quick to dismiss the talent of the tuners that have worked on this bike before you.
There have been some excellent folks and none of them have said the needles were shite is 17yrs of tuning.

Even Roger Ditchfield didn't make custom needles....... He runs the DJ needles (which are not much different than stock except for the adjustment clips) and seems to not have the issue you say all the bikes have.

With that I guess I'll just disagree with the direction you are heading as to me it appears to be a difficult solution to an issue that already has an easy answer.
Adjusting the slide speed of the front carb (and yes I am the one that first posted that tip or idea, though HRC is the one that came up with it) is a much simpler solution IMHO.


Here is something to ponder also...... Is the needle taper wrong or does the slide tend to overshoot because of how heavy it is and how fast it is moving?

[NZSpokes]

You win...... I don't have a stack of charts lying around and I tell folks to raise the needles because I guess I'm clueless as that is making the stock needles ever shorter.

The the fact that there are 100's of folks that run my carb set up ( On the other board where I first posted my set up it has 56,719 views so far) and it works just fine for the majority of folks.
Even then, it doesn't work for every bike and I claim it to be no more than a base line as you will need to tune it in to your bike.

Now for the fat spot you talk about, yes I address that issue and IMHO it is not a needle issue. It is a slide speed issue and I take care of the rich bump with my set up without the need to find one off needles.

Another hint I will give you as a carb tuner and a machinist, the only way you can accurately measure the needles is with an Optical Comparator. It is the only way you can measure the tapers.
Also the needles are hardened (or they would wear out prematurely) so your idea of modify one with sand paper is going to be difficult at best.

In the end, like I said, it is god to see the interest in a dying art.
Believe it or not I am only trying to help you out not be negative.

Another final tip, as I am not going to argue with you,
Don't be so quick to dismiss the talent of the tuners that have worked on this bike before you.
There have been some excellent folks and none of them have said the needles were shite is 17yrs of tuning.

Even Roger Ditchfield didn't make custom needles....... He runs the DJ needles (which are not much different than stock except for the adjustment clips) and seems to not have the issue you say all the bikes have.

With that I guess I'll just disagree with the direction you are heading as to me it appears to be a difficult solution to an issue that already has an easy answer.
Adjusting the slide speed of the front carb (and yes I am the one that first posted that tip or idea, though HRC is the one that came up with it) is a much simpler solution IMHO.


Here is something to ponder also...... Is the needle taper wrong or does the slide tend to overshoot because of how heavy it is and how fast it is moving?

This I agree with.

And it matches a conversation I had with our top Dyno guy and the base of our problem with the FIL mod. Which is slide control. A slide that slams open can cause a rich or lean situation. If you look under the stock air filter you will see a factory restriction. This is to keep the slides in control.

I strongly believe better control of slide speed and signal to the main fueling circuit will make the FIL mod work great. Flow commander starts to do this but a cleaver man would remove the drilled plug and thread it for jets so it can be tuned cheaply.

Right now I am on Hawks setup and it works great.

[VTRDark]

If you look under the stock air filter you will see a factory restriction.

You may very well be onto to something there.

IMO What everyone is saying is right as it really is a kinda of blackart as 8541Hawk briefly mentioned. It's like being on the path to enlightenment, there's no right or wrong way to an end goal outside of the basic rules like only making one change at a time. Then there is the differences between each bike and various mods, climate conditions etc. Yeh one can give a good baseline and it gets people started but once you start tinkering it all comes down to fine tuning and making adjustments according to any future changes. The more extreme the changes the more extreme the tuning gets.

I have been watching the goings on with the FIL mod with great curiosity. Some great research, R&R work going on with you guys. It's all mikstr's fault I'm watching the goings on there with great interest too.

(:-})

[Varastorm]

Has anyone access to Factory Pro needles?

Just thought I would ask, it any one has would they be kind enough to measure them up?

I am after the "D" measurement, if anyone can help. Thanks in advance



http://www.allensperformance.co.uk/data-n427-48.html

[VTRDark]

He's a man on a mission.

Mine are in the carbs. But if you can hold on until next weekend I will whip a needle out and measure with a micrometer. I have a busy week ahead of me but I may find one evening in the week to whip a needle out.

(:-})

[Varastorm]

Mine are in the carbs. But if you can hold on until next weekend I will whip a needle out and measure with a micrometer. I have a busy week ahead of me but I may find one evening in the week to whip a needle out.

I would really appreciate that Carl, it would be so helpful

I have been trying to cross reference needles from the Allens Performance site, nothing matches tbh.

I'll give them a call in the week to see if they can help.

I do feel confident that I could get the jetting sorted by cutting my own needle profile. But I hate putting myself in a situation were if I mess them up I have to cough up £80 for another DJ kit

My dilemma is knowing how much metal removal from the "straight" section alters the afr ratio. Also, should I file a little down the taper a little also ? Any one done this before ?

The reason I am being so relentless in chasing this lean 3000rpm issue, is that after the lean stumble clears the acceleration is really really impressive.

I really can't describe the difference groove 4 to groove 2 makes to the +5000rpm performance. The rear squats, the tyre squirms for grip & the front wheel is in the air in 1,2 & 3rd. We are talking about a 2 Ton Varadero here, not a VTR

[CruxGNZ]

I got ya man. I'll get that measurement to you tomorrow. I have FP, DJ, and stock needles to measure from.

[Varastorm]

I got ya man. I'll get that measurement to you tomorrow. I have FP, DJ, and stock needles to measure from.

Spot on CruxGNZ really appreciate that

Seeing that you've offered your help & time , could I be cheeky & ask if you could measure the "L1" measurement & total measurement (from the pic above) please

The reason I ask is the taper on those FactoryPro needles look interesting

[CruxGNZ]

I can't find my micrometer. I really don't know what happened to it. Looks like I'm buying another one tomorrow. Sorry I couldn't get you those measurements today, but I can when I buy another one tomorrow.