jetting problem/quiery...

[lonetree]

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...

[GMP]

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.

[Jakobi]

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.

[lonetree]

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?

[Jakobi]

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.

[lonetree]

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.?

[Jakobi]

Is this an opportunity for me to get creative?

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.



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.

[Jakobi]

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!

[swazi_matt]

Originally Posted by Jakobi

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!

I seem to remember someone on the forum modified a needle with good results, cant remember who though

[lonetree]

Originally Posted by Jakobi

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!

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..