jetting problem/quiery...

L

lonetree

New member
Hi,
lately i have been trying a few different jetting combinations, but after much experimenting im a little stuck.
Im trying to get my bike (ec250r, '09 ASI carb) to run on the N3xx series of needles, with my current set up a N3eg needle 2nd clip, and a 38 pilot, which i can get to idle really well, and pull cleanly off the bottom, and the air screw seems to have a lot of effect, although at 1.5 turns seems perfect.
i started this set up with a 178 main which just happened to be in the bike at the time, however it immediately showed signs of running lean from about mid throttle to wot,- higher temps, and the plug was looking like it had run too hot. The bottom end however was incredable!, snappy as, heaps of torque and pulling onto the pipe so quick.
I put a 180 in and it seemed better at WOT but the bottom end seemed to become "fluffy" loosing snap, although a little play with the air screw sort of cleaned it up a little. I also noticed that if i really twisted the throttle hard to wot whilst the engine was already reving hard, it seemed to "miss" once or twice before pulling through to really high revs. (it was doing this also with the 178 main but slightly worse)- another lean symptom i presume?????

so i went to a 182 main, top end was a little better, with the "miss" under hard excelaration now much harder to produce, but the bottom end of the rev range is now even more fluffy and to clean it up i have to turn the air screw out until the idle starts to hang...
I want to go to a 185 main but not at the expence of the snappy bottom end i first had and now seem to be loosing with each increase in main jet.
How do i get around this problem?
i do have a N3ew needle, will going up in needle diameter (and pilot jet if needed) help this problem?
im hoping the theory in my head is right, but im not sure...
 
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I think its likely the lean end taper of the N3 needle. This is well documented, and one reason JD designed his needles the way he did, very much like the N3 with a richer end taper. The needle will control the top end mixture quite a bit so you should try going a clip richer or the half clip needle option.
 
I went through this the other day with the N3EW#2. tried 175, 178, 180, 185 mains and also noticed the effect it had on the lower revs and off idle response. The lean area was indeed right in the mid range as confirmed witha plug chop. A richer main supplied more fuel here, but also more fuel everywhere else.

Your theory of going oen leaner on the needle diamter is sound and should work to liven up the bottom some more, but you'll likely still be richer than you need to be at WOT.

What I did was the same as Glenn suggested. Went richer on the needle clip position, leaned off the air screw a touch, and ran with a leaner main. Its well documented with this needle and the kato mob that once you get the bottom end clean enough to run crisp the mid falls a bit lean, or to have the mid just right you run a touch rich off the bottom. Its also this rich-lean transition that gives the bike the big hit.

JD and Suzi needles work by running leaner in the first taper, and then adding an extra taper to fill in the mid range. Its also why they are smoother in delivery.
 
would it be possable to modify the taper of a needle? say copy the last taper of a NEDW onto a N3EW or at least somthing close.
anyone ever tried this?
I do have access to a couple of very good machinist mates, might have to have a chat with them.
maybe even just chuck the needle in a lathe and do the old emery paper on a file trick....
comments?
 
For sure you could have someone machine the ideal needle. Its basically what JD has done and is making big coins off it. It might take a fair bit of trial and error to get right though and you also have to remember we are talking fractions of a mm here.
 
well, it seems i may have access to someone with the gear to be accurate enough to do this..
the real question is what needle taper do i copy?
any suggestions.?
 
Is this an opportunity for me to get creative? :D

I'd go for something like the NEDx range. But a bit leaner through the middle taper. Maybe a shallower taper, or just start the middle taper a bit later.

Needles.jpg


If you moved the middle taper of the NExx down to start where the second taper of the N3xx starts then you will get that nice bottom end, and it won't richen up until a bit later on filling in the void (read lean midrange). You then get to run a nice small main for good over rev.
 
If you want I'll get the camera, graph paper, verniers, N3xx, NExx, NOZx, and JD Red and size em all up and we can have a crack at doing a hybrid. I'd be keen at giving it a crack!
 
Jakobi said:
If you want I'll get the camera, graph paper, verniers, N3xx, NExx, NOZx, and JD Red and size em all up and we can have a crack at doing a hybrid. I'd be keen at giving it a crack!
Click to expand...
I seem to remember someone on the forum modified a needle with good results, cant remember who though
 
Jakobi said:
If you want I'll get the camera, graph paper, verniers, N3xx, NExx, NOZx, and JD Red and size em all up and we can have a crack at doing a hybrid. I'd be keen at giving it a crack!
Click to expand...

somthing like that would be great. although im thinking along the same lines, a n3xx at the top of the needle going into a nexx taper...
it would be good to compare them all.
if i can get accurate enough to have good mesurements, i should be able to get multiple needles done, although not sure if there will be a machining cost yet.. ;)
 
I don't expect anything for free. Happy to chip in to cover materials and other peoples time. I'll see what I can get done this arv re measurements. Are you happy with the clip positions and straight length of the N3xx? I find they give a good range of adjustment. They way I would describe them is that they only lack a bit as they just come on the pipe. Could use some more fuel. Moving the clip pos richer makes the bottom end too rich, going bigger on the main can clean up the lean spot at expense of over rev.
 
I would be willing to buy a needle if they are going to be a better setup than what I have now.
Jake , this is your dream isn't it?:D
Cheers Mark
 
Very interested in this.. Jakobi, if i loose track of this, can you remind me on dbw? (agent86)

Sounds like your chasing the exact problems that i am with the mods to the needle tapers and such.
 
I hoped that no one would miss my humor. Apparently my wife isn't the only one.

If any seed money or base needles are needed (assuming modified existing needles) say the word and seeds will be sown and needles volunteered.
 
wence said:
I would be willing to buy a needle if they are going to be a better setup than what I have now.
Jake , this is your dream isn't it?:D
Cheers Mark
Click to expand...

Its pretty interesting. Not what I would consider dreams coming true though. That would involve being overwhelmed by many beautiful womens beyond my reach in reality. On that topic, you know you're under the thumb or married when you wake up feeling guilty after said dreams. Haha!

Donk said:
Very interested in this.. Jakobi, if i loose track of this, can you remind me on dbw? (agent86)

Sounds like your chasing the exact problems that i am with the mods to the needle tapers and such.
Click to expand...

I'll see if I can remember. Again I don't see the N3xx needles as being bad. Really like them and prefer them over the Suzi needles for the clean bottom end and big top. Be nice just to have a little more grunt just as its coming on song.

pscook said:
I hoped that no one would miss my humor. Apparently my wife isn't the only one.

If any seed money or base needles are needed (assuming modified existing needles) say the word and seeds will be sown and needles volunteered.
Click to expand...

Haha! Your post wasn't taken seriously mate :) I was pickin up what you were putting down :D My response was more back to lonetree saying not sure if there would be a machining cost. Probably should have quoted his post.
 
i cant promise anything yet folks, it may not work out, or it may work out to be too expensive to be worth it, have to wait and see on that.... but im happy to keep people posted, and help out if possable.
as for the needles,
i really like the n3xx needles but im just worried that im going to kill my bike running too lean. i love the snappy bottom end but to get that, the mid to wot end seems too lean.

i have a n3eg and a n1eg to compare, it would be nice to see a neeg if such a thing exists...
i also have a n3ew and a nedw to compare, and i think i can get around the clip postion change between the 2. is there a n1ew/n1dw?
my inital thinking is to use a n3xx needle but change the taper on the tip 2/3 to n1xx/nexx taper.
or somthing like that...
 
I was having a think today too and thinking the same thing. If you took an N3Ex/N3Cx needle of your prefered diameter and managed to get someone accurately machine a richer middle taper in, and then leave the tip lean it would be almost perfect. Then again, it may end up just like JD's needle. LOL

I could stick a needle in a drill press and have a go with some sand paper but it wouldn't be accurate enough. You'd need someone with a machine who is willing to do the work.
 
Jakobi said:
I was having a think today too and thinking the same thing. If you took an N3Ex/N3Cx needle of your prefered diameter and managed to get someone accurately machine a richer middle taper in, and then leave the tip lean it would be almost perfect. Then again, it may end up just like JD's needle. LOL

I could stick a needle in a drill press and have a go with some sand paper but it wouldn't be accurate enough. You'd need someone with a machine who is willing to do the work.
Click to expand...

I've just been sitting in the shed looking at all my needles side by side, and thinking bout this...
and after seeing the graph you posted the link to, im almost wondering if the "perfect" needle is actually a nice curved profile rather than "tapers" which have well defined edges, almost ridges...
perhaps just a smooth out with emery paper may be the ticket, but as you said, impossible to replicate due to inaccuracies...
need a cnc lathe and actually plot a curve to produce the required taper....(DMCCA, you there????)
o god, what a can of worms to open, what have i done.... :p
 
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