I need jetting help....

[Jakobi]

Stock needles used the F diameter, most people on earlier models went to a G to clean it up. But the stock needle has a pig rich first taper and a short straight section which makes it hard to work with regardless of clip position. Thus I don't like it.

The length of the straight section and clip pos determines the extact throttle position that the needle comes onto the taper, but generally the diameter is most felt at 1/8th throttle. Between 1/4 and 1/2 throttle with biggest effect around 1/4 throttle is all clip position. 1/2 - WOT is an overlap between the needle and main.

If you really want to do some back to back testing to get a feel for the needle diameter let me know and I'll post you 3 x needles of the same taper profile with different straight diameters. (N3EG, N3EH, N3EW).

[n_green]

I had an N1EG on clip 1 in it when I got it and yep it was filthy rich off the bottom.

I've found I'm beginning to understand how the needles interact with the jetting by seeing the figures ie your post above with the diameters of the needles helped me visualize what was going on. By any chance do you have other figures/explanation for the NECx/NEDx/N3xx needles as in straight section length and taper angles?

I have an NECJ and NECW here so may try them it should give me an idea on the different straight section. Thanks for the offer though.

[Jakobi]

The lengths are pretty similar with the NEDx vs the N3Ex. x being the diameter on the straight section. All the diameters are the same across the OEM needles. The main differences in them are the taper profiles, and thats the reason why I don't think you'll ever find the grunt you are looking for with the NEDx (even with a larger diameter).

N1Ex (3 tapers) Wayy rich -> Moderate -> rich - Everyone lifts the clip position to try and overcome the rich first taper, this leaves the bike lean in the middle, the last taper provides good fuel and likes to be paired with a smaller main.

N3Ex (2 taper) Rich -> Lean - With the right diameter you can get good torquey response off the bottom with a wickid hit/transition in the mid range when it leans off abruptly. Some issues experienced that to get the bottom lean enough to be crisp you can fall too lean in the mid range. Being that there is no 3rd taper you need to use a largish main to supply extra fuel towards WOT.

NEDx (3 tapers) Lean -> Moderate -> Rich - The nature of the beast, starts lean and progressively gets richer. It means you can have good clean throttle response with no surprises in the rev range. The clean bottom end lacks torque in some applications, but also responds really well to clutch. Richish mid range smooths the hit, and the needle supplies good fuel towards WOT. Smallish main compared to N3 (same as N1Ex).

JD Needles (3 tapers) Rich -> Moderate -> Lean - Good torquey delivery off the bottom, enough fuel to be smoothish but strong in the mid range, lean towards WOT asks for a big main jet. Obviously some significant differences between red and blue. Red is more comparable to a cross between N3xx and NEDxx.

[n_green]

Jakobi you're a legend.

Received some needles in the mail from Jake the other day, finally got a chance to get out ant test it today. Picked a ripper of a day to test it, 43 deg C (109 F) 20% humidity, 350m (1150f) altitude.

The area I tested in consisted of flat fire trail with a small amount of tight single which ended with a moderate rutted rocky hill climb about 40m long with a large boulder at the end that needed to have the front wheel lofted up and over.

Also went out with a mate and we did back to back rides using the jetting for another point of view.

Stuck a 178 main and 40 pilot in the carb. Then using clip 3 for all needles tried the following:

N3EG: Inconsistent idle. Rich splutter/burble from off idle to 1/8 throttle. Slight hesitation before clearing its throat and ripping onto an awesome top end.

N3EH: Better Idle, slight rich burble off idle, smooth torquey throttle which exploded into a meaty mid and awesome top end.
Stu (my mate) didn't like this needle too much, he said it was too rich and burbly from idle to 1/8 throttle for his taste.

N3EW: Good idle, crisp off the bottom with a crisp possibly lean spot just after 1/4 throttle which then transitioned strongly again into an amazing mid and top end. This needle could have used a larger pilot however for the purpose of this test we left the jets as is and compensated with the air screw which was wound in to 1to. I felt this was a borderline needle, it was crisper and more responsive then the 'H' diameter needle however didn't obviously make any more power.
Stu loved this needle, it was his pick of the bunch, he said it didn't feel lean anywhere to him and was just smooth and strong right from idle to WOT.

N3CH: (Jake's recommendation for my bike) You've done it again Jake, this needle is fricking awesome. With the air screw at 1.25 turns it idled well, had great torque and pulled strong and clean into a killer mid and impressive top. I did feel though that the top end signed off slightly earlier then with the 'E' tapers but only right at the very end.
Stu said this needle was still slightly rich and burbled for him and the transition into the mid/top end was too strong for his liking.
For giggles we threw a 180 main in and took it for another lap, I felt it lost nothing but nor did it improve anything. I thought it was hesitating ever so slightly about 3/4 throttle maybe a rich bog but I couldn't get it to do it consistently.
Stu liked this jetting combo, he said the transition into the mid/top with the larger main was smoother due to it being slightly rich.

N3CJ:The 180 main stayed in for this test. Straight away it was obvious the pilot was too small, even at .75 it was still idling slightly high. I felt it lost noticeable amounts of torque from the bottom and was too snappy in the transition onto the pipe. With a larger pilot I may have a different opinion however given it was crisp on such a hot day with low humidity it would be useless in cooler/wetter weather.
Stu again liked this needle, it was his #2 pick of the bunch. He could tell it was lean off the bottom but couldnt pick up on it losing as much torque as what I could.

My pick of the bunch was Jakobi's recommendation - 40p, N3CH 178 main. It was ever so slightly rich off the bottom but come cooler weather/higher humidity it will probably be just right.

I would have liked to try a N3CW (didnt have one) which may have cleared up the off idle burble but given the N3EW was crisp it may have been on the lean side anyway.

I'm very happy with this jetting now, on the little test track I used it was good, I even went up the snotty rutted hill with this jetting in what I thought was second and as it just made it to the top and over the final boulder I almost had to clutch it, then realised it was in third.

It may kill me in the tight single track though, the transition is FUN, but whether I can control it in the tight stuff will test me out

Thanks again Jake, you've made me very happy, I got exactly what I wanted from this bike finally, strong tractor like torque with a good strong top end.

[n_green]

Regarding my above post Stu my mate seemed to favour the slightly leaner jetting where I favoured the slightly richer jetting. He is 20 kg lighter then me, would/could this explain why I felt his jetting was lean and he thought my jetting was rich?

[n_green]

Forgot to add the initial run with the N3EG we used a 175 main, both of us thought it may have needed a bit more fuel, in went the 178 and it was instantly noticeable that it improved the top end.

I have an oval bored 36 x 39mm ASII. Does this seem like a large main to be running in this carb? Thats almost pure 38mm main jet territory isn't it? What the hell will I do in sand or winter, 180 is the biggest main I have

[Jakobi]

I basically run a 175/178 all year around on my bike. I think the 175 might be a bit on the border, and its a 259. I'm interested to see how my piston looks when I pull it down. I'm expecting some carbon under the dome again. For an oval bore it doesn't sound too bad at all. Sounds right on par.

Really great how you provided yours and Stus feedback. I really like that idea! In my opinion it just highlights how much jetting is personal preference as well. I am like Stu where I know I give up some outright torque in exchange for clean and crisp throttle response. Using the W in mine now and its very much perfect. If I come out a half a turn more on the AS I feel the torque sign off. Half a turn in and it starts to blubber more than I like. I thought you would have liked the H

The N3CH vs N3EH should have very little effect on top end. The CH is just the half clip leaner equivalent. Its like running N3EH#2.5 - thats why it was a bit angrier in its transition.

FWW I have also found that the half a clip leaner makes a considerable difference in fuel economy. My bike would use more than a litre more over a 90km ride (N3EW#3 vs N3CW#3).

You'll also have no issues in the tight stuff. You soon learn the point where it comes on song and just ride below that until you can see ahead far enough to wick it up! Once again, thanks for the write up Nath and glad you had some positive results.

[n_green]

Jake would your 250 require a smaller main or no difference?

Makes me wonder now I was running a 170 with the JD Blue in the oval bore and it has a leaner tip diameter then the N3 needles you've sent me. Maybe I was running lean all this time.... In 15 hrs the piston will reveal all I guess.

As for today's jetting, well I'm happy with your recommendation when it's 44 degrees and 20% humidity. What changes would I expect to make if its nicer riding weather say 15-20 degrees 50-75% humidity?

[Jakobi]

If anything a smaller capacity engine requires bigger jets as it pulls less vaccuum. I'm at 300M+ all the time here and rarely below 25C and generally have substantial humidity as well. In my 300 I was running 172/175 most the times.

You'll be safe at those temps still with the 40 N3CH#3 178. It'll probaby run a touch leaner and Stu will like it more If it gets cold (ie under 10) you might want to go a half a clip or clip richer. I'd personally just ride it. You know what it feels like when its going lean so when you start to feel its losing its performance or falling flat richen it up. Just be careful you don't get caught in the loop I did where you are spending a day after each ride trying new jetting specs to try and make it perfect. I usually ended up coming back to the same place.

If you want, get a N3EH and N3CH and then you can easily make a half clip change when you want to. I actually carry a few spare needles and a clip in my tool kit. Probably not surprising though

[n_green]

I forgot that on my final run with the N3CH #3 and 178 main combo I did a WOT run in 4th for at least 500 meters. Was flat ground so not much load on the engine. Pulled the plug today and its a nice light caramel colour. That's gotta be the first time ever I've had a decent reading on a plug from doing a throttle chop.