Jetting with the Zook NECJ

[Charles De Mar]

My bike sucked at 9000 ft. 

[Doc_speeder]

So I recently jumped on this Zook bandwagon with my '16 YZ250X.  I got the NECJ and NECK to try out.  Started out with NECJ and just put it in where my N3CW was at #2.

I'm riding about 3000-6000 ft, it's been 25-30C most rides.

So I started out with:

45 PJ

NECJ #2

170 MJ

I haven't been able to do any off road as it's too dry and all the crown land is closed due to fire risk, so I've been testing at the track, trying to simulate normal single track type riding conditions ie: lots of low throttle, low-ish rpm type riding, then some open stuff, then repeat.

With those settings the bike felt dead.  Not really rich enough to burble, and still revved out clean when I got on it, but didn't seem to pull as high as with the N3CW (which I expected as the Zook needles are much thinner on the pointy end) and throttle response felt (and sounded) "thick".  That's my word, hopefully conveys what I feel it does...

Also, right off idle if I ripped it open fast, it would lean bog pretty bad.  So today I tried:

48 PJ (UP one size)

NECJ #2 (no change here)

168 MJ (DOWN one size)

BANGO BINGO.  Sweet, sweet setup.  Super snappy right off idle with no lean bog, and although 0 - 1/8th burble is still there a bit, which I don't care about at all, the rest of the throttle range and rpm range it's a fekkin rippa!  And smooth! No big hit anywhere.  The throttle feels very connected to the rear wheel, more so that any other 2 stroke I've ridden really.  Seriously, I couldn't believe the difference it made.  So I'll stick with this for now, see how it works when I actually get some single track seat time on it.

 

So my whole setup is:

-Jetting as above

-One PV washer removed

-FMF Gnarly pipe

-PC Type 296 SA silencer

-Original top end with about 65 hrs on it now

- Yamalube 2R @ 30:1 and just 91 octane pump gas. Yeah that's right 30:1.  Oil is good for your motor mmmmmkaaaay?

 

So I do have a theory about these needles related to the MJ.  I think that the thin tip of these needles brings the main jet into the equation sooner (lower throttle opening) than the Yammy needle.  I think that explains why even though I went UP with my PJ, and didn't change the needle clip the bike actually runs clean and crispy every where when the throttle was actually open.

 

Edited August 23, 2017 by Doc_speeder

[Dconer1]

8 hours ago, Doc_speeder said:

So I recently jumped on this Zook bandwagon with my '16 YZ250X.  I got the NECJ and NECK to try out.  Started out with NECJ and just put it in where my N3CW was at #2.

I'm riding about 3000-6000 ft, it's been 25-30C most rides.

So I started out with:

45 PJ

NECJ #2

170 MJ

I haven't been able to do any off road as it's too dry and all the crown land is closed due to fire risk, so I've been testing at the track, trying to simulate normal single track type riding conditions ie: lots of low throttle, low-ish rpm type riding, then some open stuff, then repeat.

With those settings the bike felt dead.  Not really rich enough to burble, and still revved out clean when I got on it, but didn't seem to pull as high as with the N3CW (which I expected as the Zook needles are much thinner on the pointy end) and throttle response felt (and sounded) "thick".  That's my word, hopefully conveys what I feel it does...

Also, right off idle if I ripped it open fast, it would lean bog pretty bad.  So today I tried:

48 PJ (UP one size)

NECJ #2 (no change here)

168 MJ (DOWN one size)

BANGO BINGO.  Sweet, sweet setup.  Super snappy right off idle with no lean bog, and although 0 - 1/8th burble is still there a bit, which I don't care about at all, the rest of the throttle range and rpm range it's a fekkin rippa!  And smooth! No big hit anywhere.  The throttle feels very connected to the rear wheel, more so that any other 2 stroke I've ridden really.  Seriously, I couldn't believe the difference it made.  So I'll stick with this for now, see how it works when I actually get some single track seat time on it.

 

So my whole setup is:

-Jetting as above

-One PV washer removed

-FMF Gnarly pipe

-PC Type 296 SA silencer

-Original top end with about 65 hrs on it now

- Yamalube 2R @ 30:1 and just 91 octane pump gas. Yeah that's right 30:1.  Oil is good for your motor mmmmmkaaaay?

 

So I do have a theory about these needles related to the MJ.  I think that the thin tip of these needles brings the main jet into the equation sooner (lower throttle opening) than the Yammy needle.  I think that explains why even though I went UP with my PJ, and didn't change the needle clip the bike actually runs clean and crispy every where when the throttle was actually open.

 

Good to hear its running awesome. On your next woods ride though, i would recommend you bring a couple spark plugs. a 48 pilot is rich with the Zook needle even at sea level. Even more so at 3-6k. If anything, there a good chance to cold foul a plug with that big of PJ and that altitude. I had the same issue as you somewhat. I put in a 42PJ and had a lean bog when i snapped the throttle but everything else was pretty dang good. (Im at sea level). Turned in the air screw to richen it up and BAM. Ran perfect. Just thought id share my experience.

[numroe]

14 hours ago, Dconer1 said:

a 48 pilot is rich with the Zook needle even at sea level. Even more so at 3-6k.

Agreed.  a 48 pilot makes no sense to me. I understand if something works, it works. But I'm skeptical about how well it works.

The general rule of thumb when going from a working Yam N3xW setup to the Zook NExJ needle is to stay on the same clip height, then go down 1 or 2 on the pilot jet size and 2 or 3 sizes on the main.  This is the safe starting point. Then fine tune from there.

As soon as I get some time (maybe Sept) I'm going to try my NExH needles, which are richer below 1/8th throttle, with smaller pilot jets. The jetting seems pretty good now but I just have to try it, and can always go back.

[Doc_speeder]

Agreed.  a 48 pilot makes no sense to me. I understand if something works, it works. But I'm skeptical about how well it works.
The general rule of thumb when going from a working Yam N3xW setup to the Zook NExJ needle is to stay on the same clip height, then go down 1 or 2 on the pilot jet size and 2 or 3 sizes on the main.  This is the safe starting point. Then fine tune from there.
As soon as I get some time (maybe Sept) I'm going to try my NExH needles, which are richer below 1/8th throttle, with smaller pilot jets. The jetting seems pretty good now but I just have to try it, and can always go back.

Believe me,I agree. But it just does seem to work. Now, with that said my a/s is 2 full turns out with this setup, and I'm not as bothered by the burble as many are, but it doesn't FEEL rich down at small throttle opening. Response is immediate and predictable. I'm riding again tomorrow evening. I'll report back if I discover anything new.

Sent from my Lenovo TB-X103F using ThumperTalk mobile app

[numroe]

On 24/08/2017 at 0:59 PM, numroe said:

As soon as I get some time (maybe Sept) I'm going to try my NExH needles, which are richer below 1/8th throttle, with smaller pilot jets. The jetting seems pretty good now but I just have to try it, and can always go back.

Done.  In my 295, I tried the H, W J and K needles. This change to the needle straight section makes a surprisingly big difference below 1/4 throttle.

For my motor, the lean K needle wins.  This is also with the lean #8 slide.

With the rich H needle, I also tried a smaller 38 pilot, and still didn't like it. No matter was air screw setting it had weird issues at closed throttle and something wrong with the response when rolling to 1/4 open. 

W with P=40 was still too much fuel. Stuttering away.

J with the 40 was back to my usual. Very good. Thought it was done, but a little sputter was still there and AS out more didn't feel right, so I thought the K needs a try.

K and still using the 40 pilot is great.  Air screw had to go in to 0.75 out. The motor pulls fine. No hesitation. Lot of fun with the consistent response.

I'm presently using a 295cc motor with 1.4mm squish and P=40, AS=0.75, SL=#8, N=NEDK-2, M=165, pwr=40. Below 500ft. 15 to 25C air temp. And it pulls crisp and very strong. Motor temp feels normal and this jetting gives great mileage on medium/slow hilly trails (with the Gnarly pipe). Will do over 90km on a stock 8.5L tank. Sweet motor.  I'm lovin it.

Edited September 21, 2017 by numroe

[LSHD]

Yep. NECK is also a great YZ needle with #8 slide and squish mod. Numroe, I think it was you who was sceptical about it when I was trying the K. Maybe had more to do with my particular symptoms. I thought I was rich and you thought I was lean. But in any case, K sure feels right.

Edited September 21, 2017 by LSHD

[numroe]

On 22/09/2017 at 1:06 AM, LSHD said:

Numroe, I think it was you who was sceptical about it when I was trying the K.

Yep, probably me. I cannot remember.

The performance with the leaner K needle surprised me because I am using it with the leaner #8 slide. Also how much better the motor is for trail riding when frequently on/off varying amounts of throttle.  The jetting clean up is only below 1/8th, however the improved response makes it feel a lot better.

Anyone riding a YZ250 (or 295) with any burble at low throttle opening should never assume it is "that two stroke thing".  It's simply jetting.

Carbs are great once tuned in. So simple and light weight. But I can totally understand that most people don't want to mess with it and therefore the potential wide attraction of fuel injection for 2 strokes.  New bike cost is a growing concern though.

 

[LSHD]

Burble - Idiot = Smooth

Was riding Wambaw solo yesterday. My goal was smooth, perfect technique, not speed. About 1/4 way through I noticed the infamous "burble" that I have fought so long on this bike (and still had a slight bit of) went away as long as I was either accelerating or completely off the throttle. Dorked around with the throttle a bit and realized "Eureka" this dumbass has been holding the throttle literally just off idle instead of completely off during both deceleration and when coasting steady. The burble occurs over about 1-2 degrees just off throttle, when I'm not giving it any gas but holding the throttle just off the bottom. Some combo of my pipe when moving and this one position causes a slight burble. Stopped doing that; problem solved.

What triggered my thoughts on this was trading bikes with Jacob429 a couple weeks ago. Last time we rode Wambaw we swapped bikes a couple times. His is a 2018 Beta 300 RR. In reviewing the video from that ride I noticed I was sometimes getting a similar (maybe worse) burble while riding his bike. Didn't really notice during the ride, but it was clear on the video. I also noticed it was during what should have been a totally closed throttle (decel before a turn). If I think about it, almost every 2S I have ridden will have a slight burble if you hold the throttle just off idle, not enough to accelerate but not completely closed. Not sure if that is your experience or not.

All that clicked during this last ride, and like magic, goofy burble gone.

Edited October 14, 2017 by LSHD

[numroe]

For sure it impacts some riders more/less depending on throttle use.

However the burble shouldn't be there no matter how you use it.

Even if you don't care when riding, the top end will stay clean if it's fixed.

What needle (last letter), slide nbr, pilot size, pipe and muffler do you presently use ?

 

 

[LSHD]

It was there on both bikes, YZ250 and 2018 Beta RR. Are you saying there is no amount of throttle near zero that burbles on your bike? If you just barely crack it, can you make it burble? My guess is that you can, but maybe you can't.

Here is what I am running. Temps are 80 degrees F and about 85-90% humidity.

170 main, #8 slide, 0.050" Squish, NECJ#3, 45 Pilot, Stock Reeds (new), Float set properly, Air Screw does not eliminate this.

Best response is what you saw in my video a couple months ago, NECK needle on 3. But during that ride I had a lean rev or stuck throttle and that led to my complete rebuild. Haven't tried any new jetting since the rebuild. Next change I make will be trying the NECK again, then 42 pilot if necessary.

[numroe]

35 minutes ago, LSHD said:

Are you saying there is no amount of throttle near zero that burbles on your bike? If you just barely crack it, can you make it burble?

Correct. It never burbles. I roll it open and it pulls clean and predictable.

However both my 249 and 295cc top ends have lower transfer ports (reduced port timing) vs stock. Shave base on the 249 and all 295 built by big boring the stock cyl have lower ports. So that no doubt helps them pull cleaner and stronger down low. They still rev more than I need.

I aim for broad power in my 2 strokes. So more 4 stroke like in terms reduced gear shifting and increased fuel economy, but with the big 2 stroke benefits of way more agile handling, no stalling, less weight to lift around at times, and the sound is sweet and doesn't travel far at all.

35 minutes ago, LSHD said:

Next change I make will be trying the NECK again, then 42 pilot if necessary.

Excellent. I'm curious to learn how that goes. Might be good.

[Bren Ledger]

On 10/14/2017 at 6:48 PM, LSHD said:

It was there on both bikes, YZ250 and 2018 Beta RR. Are you saying there is no amount of throttle near zero that burbles on your bike? If you just barely crack it, can you make it burble? My guess is that you can, but maybe you can't.

Here is what I am running. Temps are 80 degrees F and about 85-90% humidity.

170 main, #8 slide, 0.050" Squish, NECJ#3, 45 Pilot, Stock Reeds (new), Float set properly, Air Screw does not eliminate this.

Best response is what you saw in my video a couple months ago, NECK needle on 3. But during that ride I had a lean rev or stuck throttle and that led to my complete rebuild. Haven't tried any new jetting since the rebuild. Next change I make will be trying the NECK again, then 42 pilot if necessary.

I also have this exact "issue" my 250x runs extremely well and has very good power delivery and response from very small throttle openings all the way up to a very good over rev. I'm using the NECJ (3) with a 45 pilot and 170 main jet @1k  I have the same "burble" at very small throttle openings if I hold it there steady but so minimally that I don't notice it while riding.. Only in a "cruise" type situation.

I also have a stumble when coming down off throttle when the bike is rev'd in neutral that's not noticeable when riding that i can't seem to adjust out with the air screw. I'm using the slavens air screw that is easier to adjust by hand.

Using a turbinecore 2 sparky with the stock pioe and powervalve mod. 

Edited October 20, 2017 by Bren Ledger

[LSHD]

Really close to what I run (same pipe). Happens on either standard or X CDI. Like you said, it's right there at a fraction off idle, not hard to ride with.

[Bren Ledger]

3 minutes ago, LSHD said:

Really close to what I run (same pipe). Happens on either standard or X CDI. Like you said, it's right there at a fraction off idle, not hard to ride with.

I have tried the NEDJ (2) and didn't care for the way it affected my midrange delivery.. Made it feel weaker. 

If the NEDJ (2) is 1/2 clip leaner then NECJ (3) where does that put the NECK (3)? 

[kxrob]

8 hours ago, Bren Ledger said:

I have tried the NEDJ (2) and didn't care for the way it affected my midrange delivery.. Made it feel weaker. 

If the NEDJ (2) is 1/2 clip leaner then NECJ (3) where does that put the NECK (3)? 

NECK is the next step lean on the very starting diameter then the NECJ

everything else is the same

[numroe]

If the NEDJ (2) is 1/2 clip leaner then NECJ (3) where does that put the NECK (3)? 

K is leaner than J at 0 to 1/8th throttle. NECK-3 is worth a try.

[LSHD]

True. NECK was pretty good in my bike too. 

[mcgradybrandt]

On ‎8‎/‎23‎/‎2017 at 7:59 PM, numroe said:

Agreed.  a 48 pilot makes no sense to me. I understand if something works, it works. But I'm skeptical about how well it works.

The general rule of thumb when going from a working Yam N3xW setup to the Zook NExJ needle is to stay on the same clip height, then go down 1 or 2 on the pilot jet size and 2 or 3 sizes on the main.  This is the safe starting point. Then fine tune from there.

As soon as I get some time (maybe Sept) I'm going to try my NExH needles, which are richer below 1/8th throttle, with smaller pilot jets. The jetting seems pretty good now but I just have to try it, and can always go back.

I am still trying to understand why some people are saying to go down on the PILOT jet when switching to a Suzuki needle. I agree about the main jet, but totally disagree about the pilot. An N3EW is the same as an NECW on the starting diameter, but the the Suzuki needles have a slightly longer straight section before the first taper of the needle. I also believe that the first taper of the Suzuki needles are slightly shallower than the stock KTM and Yamaha needles (N8RX, N3EX, N3CX etc.) This is backwards thinking to say that a Suzuki needle requires a smaller pilot. Many people also find the Suzuki needles a bit lean at small throttle openings and report a hanging idle or surging especially in cold weather. Generally speaking I run a slightly larger pilot, turn in the airscrew a bit, or turn my idle down when using a Suzuki after switching from a stock Yamaha needle. One of the things I don't like in a 250 with a Suzuki needle is the loss of punch off the bottom when compared to  a Yamaha or JD needle since the Suzuki needles are generally a bit leaner up to about 1/8 to 3/16 throttle.

Edited October 20, 2017 by mcgradybrandt

[mcgradybrandt]

***the first taper of the Suzuki needles is slightly shallower