Needle/Main Jet relationship = Slightly confused

[GGRider01]

Currently the bike is running better than ever but clip position testing, out of curiosity, has me confused.

Current arrangement:

42P
NEDH, #2
172

I thought I'd try and go one step richer on the needle, since I started in #2 when I put it in. It became a sputtery mess in #3. With other setups, changing needle clip position only seemed to change half throttle behaviour, and very little in the way of noticeable full throttle behaviour.

#3 position would not allow the bike to rev out even after a lot of running around. It was just doggish past half throttle and sputtered endlessly.

I can easily throw jets in and test for myself, but at this point I don't think I know what I'm doing exactly. Would the needle position testing suggest a leaner main jet? Or something else? Interesting note: I can go up to a 175 and even a 178 with no sputtering but less over rev, but a clip change throws everything out of whack so drastically.

 

[Jakobi]

That depends on what you've changed to or from.

The relationship is that the main jet flows fuel into the nozzle. The needle interfaces with the nozzle and restricts the amount of fuel that can flow past at a given throttle position.

A full clip position is a pretty crude/significant change in fuelling compared to a main or pilot change.

Add to that, different needles series can have different taper profiles.. they provide different amounts of fuel at different throttle positions compared to other needles of different series. The Suzuki NE needles provide a lot of fuel through the mid, and even more towards WOT. Especially compared to a Yamaha/KTM N3xx series.

It's likely the case that you are simply seeing too much fuel through the mid and it's not allowing it to clear into the top end.

 

[swazi_matt]

That depends on what you've changed to or from.

The relationship is that the main jet flows fuel into the nozzle. The needle interfaces with the nozzle and restricts the amount of fuel that can flow past at a given throttle position.

A full clip position is a pretty crude/significant change in fuelling compared to a main or pilot change.

Add to that, different needles series can have different taper profiles.. they provide different amounts of fuel at different throttle positions compared to other needles of different series. The Suzuki NE needles provide a lot of fuel through the mid, and even more towards WOT. Especially compared to a Yamaha/KTM N3xx series.

It's likely the case that you are simply seeing too much fuel through the mid and it's not allowing it to clear into the top end.

So if you have a rich mid the best (only?) change is to go leaner needle type?

 

[GGRider01]

If anything, I feel the mid throttle is a tad lean. For instance, if the bike is cold, it will rev nicely at half throttle but sputter on full throttle. Once it's warm, of course full open performs as expected, nice and clean.

I'm wondering how to richen the mid without getting a blubbery mess on full throttle that a clip position causes.

As it stands, the bike is very much acceptable. I'm just trying to get a further grasp on what's what so I started moving things around. It would be nice to liven up the mid section without hindering top end.

 

[Jacob 'Berg]

If anything, I feel the mid throttle is a tad lean. For instance, if the bike is cold, it will rev nicely at half throttle but sputter on full throttle. Once it's warm, of course full open performs as expected, nice and clean.

I'm wondering how to richen the mid without getting a blubbery mess on full throttle that a clip position causes.

As it stands, the bike is very much acceptable. I'm just trying to get a further grasp on what's what so I started moving things around. It would be nice to liven up the mid section without hindering top end.

If that is the case, maybe a different taper and/or diameter needle, which would clear up the transition onto the main jet.

 

[barossi73]

Nech is halfclip leaner than nedh.
I also found nedh#3 too rich/sputtery and nedh#2 a little flat.
Nech#3 is right inbetween and works very nice on my 200.very occasionally (once) sputters when it gets a little hotter than usual.concentrate on how it runs fully warm.if it runs good cold it will likely splutter and choke when it gets to normal temp

 

[barossi73]

Is the 'h' the same diameter as your stock noz? or n1e?
the 'w' and 'j' diameters are typically 250/300(i dont recall which is which!)

 

[Jakobi]

Nech is halfclip leaner than nedh.
I also found nedh#3 too rich/sputtery and nedh#2 a little flat.
Nech#3 is right inbetween and works very nice on my 200.very occasionally (once) sputters when it gets a little hotter than usual.concentrate on how it runs fully warm.if it runs good cold it will likely splutter and choke when it gets to normal temp

This. Half clip adjustment.

The main will have some influence across the board as it regulates the supply to the nozzle.. but this will have a more pronounced effect as the needle taper allows more fuel between the needle and nozzle.

 

[GGRider01]

My methods have certainly changed since I first set out. The first thing I look for after a change is that the bike sputters when cold since it will clear up once hot. Wide open is, I suspect quite close if not still a tad rich, overrev isn't great. 175 on the main made it slow to hit 80. 172 is quite good.

Half throttle is concerning since it's strong cold and a bit flat once hot. A little lean.

Needle diameter affects which portion of the throttle opening? It might be interesting to try the G diameter again to get a nice fat mid but I'm afraid I'll have to go very lean on the main to clean up wide open position.

Only one way to find out but thoughts are appreciated. NECH on order.

 

[GGRider01]

Is the 'h' the same diameter as your stock noz? or n1e?
the 'w' and 'j' diameters are typically 250/300(i dont recall which is which!)

No idea. Stock was a N1ED and it was all around pretty awful gutless spooge machine.

Testing the NEDH in #1 position revealed a dramatic improvement throughout, half throttle still isn't what I'd like. Zipped around town and it never felt flat, just a bit at mid. Testing might indicate a size down on the main, NECH will definitely be an improvement and not require the size down on the main to keep it away from the #1 position like the NEDH.

 

[GGRider01]

That depends on what you've changed to or from.

The relationship is that the main jet flows fuel into the nozzle. The needle interfaces with the nozzle and restricts the amount of fuel that can flow past at a given throttle position.

A full clip position is a pretty crude/significant change in fuelling compared to a main or pilot change.

Add to that, different needles series can have different taper profiles.. they provide different amounts of fuel at different throttle positions compared to other needles of different series. The Suzuki NE needles provide a lot of fuel through the mid, and even more towards WOT. Especially compared to a Yamaha/KTM N3xx series.

It's likely the case that you are simply seeing too much fuel through the mid and it's not allowing it to clear into the top end.

In a WOT condition, how much affect would the needle have on fuel flow?

I've been testing G H and W needles, both Yamaha and Suzuki.

I found that when testing all NExx needles in #2 position, they required a 172 main due to the very rich final taper. All of my N3xx needles in #2 position prefer a 175 main if not richer. Don't have anything higher. The preference isn't a strong one, though. Tests were only performed in 1 2 and 3 positions and #2 gave best results except for the half clip variants which result in a preference for 2.5 position.

Only the change from NExx needles #2 to #3 provided such a huge rich condition.

Changing clip positions with the N3xx needles yields much milder results, at times I'm unable to tell the difference.

In any case, top end pulls best with the N3CH, #3 with the 175 main. I'm disappointed with the 300 since it pulls so mildly compared to other 2 strokes I've had and it doesn't seem to improve by much, nor hinder by much. It is not currently a 40+ hp machine, no dyno needed there. It's pretty baffling to me, the filter is clean, reeds seal nicely, compression is 190+ after being ridden, and the exhaust is unrestricted. No clue.

 

[Jakobi]

The diameter of the needles straight section will have no effect on WOT.

The final taper and to some extent the clip position and how far it can lift out of the nozzle will effect WOT.

 

[GGRider01]

The diameter of the needles straight section will have no effect on WOT.

The final taper and to some extent the clip position and how far it can lift out of the nozzle will effect WOT.

I realize that the straight section is only sitting in the needle jet at low throttle openings and at idle. The H just provides the best transition from the pilot to main. The half clip variant at #3 further refines that. What I don't understand is why there is a huge lack of power despite dialing this in and changing pilots from lean, hanging idle, to a fat burbly mess. At no point between does it just leap up and go.

Most troubling is that the bike just falls flat on its face when the powervalve opens. It doesn't help that it takes its sweet time getting to that RPM from a stand still.

I don't mean to imply I know everything and quite clearly the opposite is true. I'm convinced the answer lies within the carb though.

 

[Jakobi]

Why are you certain it's the jetting?

 

[GGRider01]

I've been through everything else - short of a new CDI and trying a new carburetor. I suppose there's a small potential for some defect or clogged circuit I'm not seeing.

From intake to exhaust and fuel. Including the PV, which may be opening a bit later than I like. Another small gain to be had there.

 

[Jakobi]

Don't you have a 13' jug on an older bottom end? Did you compare the port positions between new and old? Is it possible that over the years the factory has adjusted the ignition curve to suit port changes and that the particular combo you have isn't working well together?

I understand it must be frustrating, but it's got to be something.

 

[@enrico@]

The PV has to open at the right time: too early and the motor hole, too late and the engine "Walls".
The Pv must be clean everywhere and must also be clean the housing.
The spring must be in good condition, though unnerved the PV opens early.

That said to me you're lean (what year is the bike?)
This setting ( n3ch 3# 175 ) does not have medium range power.
The candle is?
Check after an hard climbing done at full throttle!

Changes in the needle position of a notch is a very marked change, especially at small openings should be compensated with a different ending letter (straight diameter).

 

[GGRider01]

Not lean.

A 178 results in a black plug.

175 is still dark. 172 was dark, but offers consistently the best results with the Suzuki needles. Anything leaner offered no power gains and more heat.

I'm running the AS1 carb on a 2000 XC 300. This is a taller carb and typically requires richer settings than the AS2, but not in all my frustration have I been more sure that these settings are as close to the correct A/F mixture I'm going to get without a professional going through the thing.

Despite what I said to Jakobi, I'm inclined to believe he's onto something about the motor being at fault. Or more accurately: I'm at fault

I'm not even vaguely familiar with the topography or climate of Italy, but I bet you it's considerably different than my 4600ft and 25% humidity which I imagine is playing a part in why I have slightly leaner settings than most people. I've deviated a couple times now, and seem to find my way back to the H diameter giving the best result.

For now, I have a few things to go through before worrying about the jetting any more..

 

[Jakobi]

I have a 10' barrel here that I can measure if you wanted to take some comparisons.

 

[@enrico@]

Reading a bit 'of what you wrote you have always complained about the lack of pull in the middle range (lean).
Also laments the burble that you have corrected by lowering the needle.
You say that you seem to have a leaner setting of many others.
Rightly say that AS1 is leaner (at lower end I say) than AS2. It'S a 38 mm right?
By adding a bit 'of things I understand that you went from N1Ex to NECx or NEDx especially to eliminate burble and now you are with N3Cx without being satisfied.
I am the last of the last, but (of course without trying the bike) I am convinced that you are looking for cleaning without taking into account that the pull comes from below and then the final letter "H" combined with the rest of the setting is lean!
Have you checked the color of the plug immediately after an hard pulled uphill?
I struggle to believe it may be the color you say
A slight burble at constant gas is physiological and holds "the engine loaded" to meet fast gas openings (it would be different with accelerator pump: for if you have it?).
The other bikes, the ones you say pushed more, they were in place from stock, or did you have to get your hands?

4600 feet is 1400 m above sea level, in Italy we get there without any problems
25% humidity is an excellent value that we hardly reach and should you to allow excellent combustion of greater quantities of petrol achieving excellent torque and power as to compensate for the altitude.

I can not follow the talk of "porting" in combination with the ignition and the CDI because of my scholastic English, maybe the problem is.

Good luck