I need jetting help....

[n_green]

Tried the red needle today. Feels a lot 'crisper' then the blue needle.

Literally swapped needles, so went from 38p AS1.5to, JD Blue #3, 168 main to a JD Red #3 same jets. Bike idled HIGH. I wound the air screw in to .5 and then had to back the idle screw out 1.5 turns as well With this setting the off idle response was good with no hanging or running on. Obviously I should have gone to a 40 pilot but was out on the trails without any jets so pushed on.

There is a lean spot about 1/2 throttle. It's only there briefly, but the bike becomes obviously noisier and without making power at this throttle position if rolling through the rev range slowly. This lean spot was only present here and no where else in the rev range, should have raised the needle to clip #4 but again was on a ride and couldn't be assed.

The bike had also lost a lot of the torque it usually has right off idle and was more prone to stalling. A larger pilot probably would have overcome this.

The top end felt good, was definately leaner then it was with the blue needle, but I wouldn't call it lean. Crisp is probably a good description
Seat of the pants and from idle in 3rd gear drag races with my mate on his Pumpkin 300 (which has always pulled at least 3 bike lengths on me once it hits its top end) proved this. He was lucky to be 1 bike length in front of me.

Fuel economy improved as well, not a huge difference, used 8.6l for 90k's of riding, mostly single/twin trail with about 10k's of fire trail transport at the end of the ride.

Not sure if I like this needle. To evaluate it properly I'd have to drop in a 40 pilot and raise the needle one clip. I may do this before I make up my mind about it but as is it feels to lean in the middle for my liking.

 

[Jakobi]

I think that the backing of the idle screw down or higher idle means you were closer to where you needed to be. The 38 pilot was possibly too lean and you may find better results with the 40. I think JD actually recommends 40 JD RED#4 170 as the starting position for a 36mm in a gasser too. It could very well be where you want to be.

 

[n_green]

I think that the backing of the idle screw down or higher idle means you were closer to where you needed to be. The 38 pilot was possibly too lean and you may find better results with the 40. I think JD actually recommends 40 JD RED#4 170 as the starting position for a 36mm in a gasser too. It could very well be where you want to be.

I was thinking that. I set up the idle as per your method with the carb out. With the blue needle no matter what pilot I had to lift the slide with the idle screw by about 1.5-2 turns in.

It idles as good if not better then it did with the blue needle and idle screw set in the preferred range so with a 40 pilot should be right where I want it.

I'll try those settings, but will leave the main as is for now.

Thats going to change very soon anyway, my mate wants his old carb back. He says the oval bore is too powerful Said it has improved power in his bike everywhere, but especially his top end and it is just plain scary now

I'm happy with the tests I've done on the head by now anyway so be interesting to see how the carb improves things

 

[n_green]

Changed to a 40 pilot jet, air screw adjusted to 1.25 turns seemed to be pretty close although even then on occasion the 'rev method' of tuning the air screw would result in a slight hesitation/bog.

Rode it with those settings - 40P, AS1.25to, JD Red #3, 168 main. Left the idle screw alone. When hot the bike idled quite low, so low on some steep downhills I thought it had stalled it was that quiet, it also didn't like really slow speeds in gears.

The bottom is slightly better then with the 38 pilot, although it still lacks the torque of the blue needle and required noticeably more clutch to get it to pull up steep hills in second gear. It even stalled when lugging it right down which it never did with the blue needle.

On downhills especially steep first and second gear descents I noticed a lot of pipe bang (what exactly is this a sign of if anything?) Mainly occured when the throttle was closed and I was using the engine to brake (as much as can be done with a 2smoke) down the hill.

Again, thinking may still be lean, I do have my head modded and squish corrected which usually requires one step richer pilot correct? I'll throw a 42 pilot in it next weekend.

Fuel economy improved again - used 7.5l of fuel for 85k's riding. 65k's of that was tight singletrack with loads of hills, some snotty most 2nd gear. The last 20 was fire trail/tar road.

Still not sure if I like this needle. It seems to deliver the power in a 'peaky' fashion, not buttery smooth like the blue needle, which makes it hard to ride with finesse through the tighter single.

 

[n_green]

Stuck a 42 pilot in on the weekend, air screw ended up at 2 turns out. Left the needle and main the same.

The bike gained a fair bit of torque compared to the 40 pilot however was still prone to stalling right down low in the rev range. Tractoring up hills in second and even first was much improved over the 40 pilot.

It's slightly rich off the bottom now, the 40 pilot was the 'ideal' pilot but it was too crisp and was terrible for tighter technical sections. The 42 being slightly richer has calmed it down enough to make it useable in tight technical terrain now.

The transition from bottom through mid to top now goes rich, borderline rich, crisp/lean. When winding it on you can feel its doughy off the bottom, starts clearing its throat and pulling through the middle then really cleans up and pulls hard up top.

Fuel economy was 7.2l for 75k's 65k's of that was 2nd and 3rd gear single/twin trail with some gnarly hills thrown in.

In short I don't like this needle, it is too snappy for the type of riding I do and I have to abuse the clutch too much in technical terrain. It also only gets marginally better economy then the blue needle which was awesome compared to the red needle.

This is my final jetting run with the 36mm carb, the oval bore will be going in it now, think ill start with the blue needle for comparison and then play with Suzuki needles later. Won't bother with the red needle again.

 

[n_green]

I still can't get this plug chop thing happening.

Kept the blue needle in today and done a few WOT runs.

Found a decent steep hill (on tar) and from 1/8 throttle snapped the throttle open WOT in 4th gear, probably for 200m or so then shut it down.

First run was using a 170 main. During the run I could feel it load up off the bottom and then clear itself through the mid and rev cleanly into the top end. The electrode end of the ceramic was a grey colour which means lean right

Threw a 180 in it just to see. The bike loaded up more and was more obvious/slower to clear up/transition into the top. What is weird is that the ceramic was the same colour?!

Stepped down through the mains 180, 178, 175, 172, 170, 168, 165 each time looking at the ceramic but mainly trying to feel any change in power.

The 168 and 165 plug chops were slightly better coloured, still grey ish but maybe a hint of caramel in there?

I think the 168 main was the best, it unloaded and revved quicker, the 165 seemed to rev as quick but may have lacked power compared to the 168. Would have liked to have tried a 162 but 165 is the smallest I have.

Then the cops turned up (nearest house was several hundred meters away) because someone had complained, they couldn't do anything I'm registered, licenced and wasn't breaking the speed limit, but they were pretty good about it and asked that I go elsewhere even further from houses so they wouldn't constantly be getting complaints. I was done so went home.

Also, noticed the bike wasn't idling at all with a 38 pilot, even after winding the idle screw 3 turns in. Put a 35 pilot in and returned the idle screw to normal and it idles again. Air screw is roughy 1.5 turns, but I'll have to play with that another day. Also haven't ridden the bike real world yet to see what the power is like now I've made all these changes.

Does this current jetting (168 main, 35 pilot JD Blue #2) sound too lean? (36mm oval bored carb)

Really can't figure this jetting out

 

[Jakobi]

Welcome to the mind bong.

Fuels and fuel additives can influence the colour of the plug to a certain extent too. I found it really hard to get good plug readings using GRO.

There are a few other tricks you can pull out of your hat. If you do a WOT run under load for a bit and then pull the clutch and drop the throttle do the revs drop immediately? If not you're a bit lean. If you run WOT under load and then very slightly back the throttle off. Like just a smidge, does the bike feel like it surges forward or does it immediately slow. A small surge indicates lean. You can also do things like reading the fuel ring at the base of a new spark plug. That means sacrifing the plug (doing a single WOT run and then cutting the threads off).

At the end of the day you won't do too much damage being rich. You will nip an engine up if you run too lean. A rich main will splutter as you whack the throttle open in 3rd gear. A few sizes smaller will be the good spot. Running on the edge of perfection doesn't leave much room for error in the event that you get a cold morning or a load of deep sand.

I'd expect the 168 to be just about perfect for a 36mm carb, but you'd also expect the 39mm oval bore to want more fuel.

 

[n_green]

Argh can't wait for a smart carb.

I always thought the 168 main in the in modded 36mm could have been dropped to a 165, especially when the weather started getting warmer. By that token one step richer being the 168 is probably what is required in the oval bore. It probably is on the edge of safety and that was testing it on a 28degree day with no humidity at 150m above sea level.

Ill be riding this coming Thursday at 1100m above sea level. Forecast is 23
Degree C and 90% chance of rain so probably mid to high humidity. Slightly cooler and more humidity but above 1000m asl. Fug it ill run with the 170 to be safe.

I'm only persevering with the blue needle cause I don't have time to play with Suzuki or the N3CJ needles I have.

I should be right with the 35 pilot though huh?

 

[Jakobi]

I real time riding a couple sizes large on the main shouldn't make too much difference assuming everything else is where it needs to be.

If the bike idled on the 35 pilot with the blue needle that sounds about right to me. Especially considering the heat and humidity we're getting. Another bloke here with a 2011 EC300 stock engine 38mm PWK has been happy running the 35 N1EG#3 (maybe 2) 172 and all he has is a slight burble between 1/8th and 1/4 throttle. I found his bike well boring in comparison to mine though. Each to their own

Remember WOT is predomidantly in effect from 1/2 - WOT with most noticable effect from 3/4 - WOT. I'd personally be looking at the response and pull in this throttle range rather than the time it takes to start pulling after whacking it open from 1/8th. In reality you aren't going to smash it wide open from that point too often and even in that instant it still passes the whole length of the needle which is supplying varying amounts of fuel. If you really want to get a grasp for it take the main out and go for a ride with no main in there. You'll get an idea of how it does have an effect over the entire range, but where its supplying the most and what it feels like when its drowning in fuel.

 

[n_green]

Was still too rich with the JD Blue on the ride the other weekend.

Idle was pretty good it rarely stalled on me even with the clutch in on steep technical downhill sections, air screw was about 1.5 turns. Probably could have turned it out a bit more as it did hesitate ever so slightly off idle once it warmed up.

I think the main was spot on as once it got on the pipe it screamed and pulled nicely.

Remembering this was all at 1100m and on a 28 deg C day.

The JD Blue in clip 2 still broke up rich from off idle until 2/3 throttle, it has to be the diameter of the needle right?

Jakobi you posted this info over on DBW:

From my notes:

I have kind of worked out a break down of the OEM Needle codes.
N-X-Y-Z (N3EJ) (NEDW) (NOZI) (N1EF)

N - OEM Needle identifier
X - Taper profile
Y - Clip position/length
Z - Diameter

The X/Y doesn't seem to share any common ground between needles. 3 seems to be yamahas 2 taper needle. E is suzi's 3 taper, O is ktms 3 taper, 1 is the stock GG needle also a 3 taper. I'm not sure if the tapers are the same between the NOZ/N1E. They do feel very similar. The Y part which indicates clip pos/length is also paired up with the taper profile (x) to form a needle with the same properties that allows for half clip adjustments. Exmaples N3Ex/N3Cx, NEDx/NECx. I have a feeling NOZx/N1Ex is the exception and are half clip different using the same taper.

Z is the needle diameter of the straight section of the needle. It covers idle to 1/8-1/4 depending on the needles taper profile. Sizes range from:

Nxxx needle diameters
D=2.685mm
E=2.695mm (JD Blue)
F=2.705mm
G= 2.715
H= 2.725
W/I=2.735 (JD Red)
J= 2.745
K=2.755

If I'm not happy with the JD Blue as its too rich a diameter and not happy with the JD Red as its too lean a diameter (though I am yet to try the red in the oval bore) should I be looking at trying a F or G diameter?

 

[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]

I'm so close I can smell the premix

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.