Suzuki needles, pilot jets and idle........

[Simmo737]

This all starts when I bolted on an s3 high high head on my 2011 ec300e it comes with no jetting help.

Get some advice from Scotty's spares who say try a touch richer.

I have a 36 mm ASII kehin carb, the stock jetting I received was 40 N1EG 175 which is good for a stock 300 with 38 mm carb...rich for the stock 36mm due to its restricted size and higher vacuum speed (thank you mr Bernoulli) or "signal".

The 36 usually needs one step richer on the needle as well.

Bolt the the higher comp, tighter squish head on and its about right, good plug colour etc, but not a great needle imho. Good idle though, no run on into corners, no hang just dung dung dung.

I go buy a jd kit.

In goes the blue needle pj and mj one step richer than his recommendations, 40 pj all good except idle, go up to 42 pj and good idle. It's better than stock and is apparently close to or the same as the n3ch yammy needle. Very grunty.

Jakobis Suzuki needles and his thorough research spike my interest as I'm after a linear needle for tight st and logs etc. it's pretty different being lean lean rich instead of rich lean like the jd/n1

I can't get a stable idle at 42pj with this leaner again needle and get a rich bog with any more than a 165 main, so I go to 45pj, clip 2 165 and idle, plug and response is perfect and I can vary my jetting with the airscrew for alt temp.

Rm 250's have roughly the same comp ratio as the s3 head and a 38 mm carb, so they should be I step richer than me except the needle which should be one step leaner.

I found that united states stock rm 250 jetting is 50 clip 3 NECJ 168, and in SoCal ( much like my climate) they use 45/48 clip 2 NECJ 168/5. Seems to validate my jetting. Yammies also seem to use bigger pj's.

Imho our motors are more like jap motors than ktms for jetting, ktms some how can use super lean pilots, I don't think we can.

 

[Jakobi]

Not a bad read mate.

One thing that stands out is your comparison between N3CH vs JD needle. From all accounts I have heard the N3CH ~= JD Red, and that the major difference between JDs needles Blue and Red are the needle diameter (0-1/8) throttle. Now considering that the pilot is also mainly active in this area you find yourself in a bit of a catch 20 that the right pilot for the job is also dependant on the needle diameter you choose. Then to further complicate matters you have the slide cutaway which is also primarily active in this area. It makes for a very interesting struggle looking for the perfect conditions where all exist in harmony.

Now the slide is usually the constant as not too many go about changing these ($$). The rest are quite cheap. My experiences are that the pilot and needle need to be matched correctly to provide an effecient idle as well as good throttle response. For me this is a 40 and a W diameter. This puts me within the 1.5 turns on the AS without too much burble. I have also used 42P and a J diameter but feel that this leans off a bit too quickly when coming onto the needle when the pilot is opened enough to sustain a happy idle.

I have also experienced all sorts of issues trying to find the perfect balance. IE with the slide barely open I find the revs will raise when leaning the AS which indicates that I'm going the right way, but then if I lift the slide a little further with the idle adjuster screw I will experience a hanging idle, and then have to richen the circuit again which in turn drops the idle speed. To lift the slide high enough to sustain a good idle without a hanging idle I have to fatten the circuit up to the point that it then runs quite burbly on the pilot and into the needle diameter.

I have also had settings where my bike has idled well and not hung, but will bog when cracking the throttle from idle on the stand. If the revs lift ever so slightly before cracking no bog present. Not sure if this indicated a lean pilot, or just the result of a super low idle.

In part I think the slides without the windows are more prone to this than the ones with. I have a #7 slide with no window.

 

[Simmo737]

I think the Suzy use the same slide, but I agree, it's all interconnected, you can't expect to change a needle without it affecting even the idle, maybe the slide etc. it's a really challenging area. Especially this bike.

 

[Jakobi]

Further to last I also agree that our bikes emulate the japs alot more than the KTMs. I have found that my bike at these conditions is very similar to those of yz250 (or even more so yz290) owners in the states.

I honestly even found 42 N3CJ#2 172 slightly rich at 1/4 throttle a few days ago. Fantastic everywhere else. I have read of plenty of people using this. For example weather details for my last ride was average temp of 30C, humidity ranging between 80-90%. Reported as feeling like 36C. Then mix in 300M elevation and I've got me some leaner than most jetting.

Think I'll be going back to a 40P with N3EW#1 next ride as it appears to be the best for this time of year. Last year I ran 38 N3EG#1 with a 175. Had to wind in the idle adjuster quite a bit to sustain an idle and had far too much burbling right off idle. Great everywhere else.

 

[lankydoug]

I have run in to a similar problem with the Mikuni on my Husky. It would be perfect on top but lean when transitioning off the pilot or the reverse if you dropped the needle one notch. I went to a needle with less taper, in other words the second step on the needle didn't narrow up as drastically. This completely solved the problem. I know it's a different carb but the principals are the same.

I hope this makes sense and helps.

 

[Selvagem]

Not a bad read mate.

One thing that stands out is your comparison between N3CH vs JD needle. From all accounts I have heard the N3CH ~= JD Red, and that the major difference between JDs needles Blue and Red are the needle diameter (0-1/8) throttle. Now considering that the pilot is also mainly active in this area you find yourself in a bit of a catch 20 that the right pilot for the job is also dependant on the needle diameter you choose. Then to further complicate matters you have the slide cutaway which is also primarily active in this area. It makes for a very interesting struggle looking for the perfect conditions where all exist in harmony.

Now the slide is usually the constant as not too many go about changing these ($$). The rest are quite cheap. My experiences are that the pilot and needle need to be matched correctly to provide an effecient idle as well as good throttle response. For me this is a 40 and a W diameter. This puts me within the 1.5 turns on the AS without too much burble. I have also used 42P and a J diameter but feel that this leans off a bit too quickly when coming onto the needle when the pilot is opened enough to sustain a happy idle.

I have also experienced all sorts of issues trying to find the perfect balance. IE with the slide barely open I find the revs will raise when leaning the AS which indicates that I'm going the right way, but then if I lift the slide a little further with the idle adjuster screw I will experience a hanging idle, and then have to richen the circuit again which in turn drops the idle speed. To lift the slide high enough to sustain a good idle without a hanging idle I have to fatten the circuit up to the point that it then runs quite burbly on the pilot and into the needle diameter.

I have also had settings where my bike has idled well and not hung, but will bog when cracking the throttle from idle on the stand. If the revs lift ever so slightly before cracking no bog present. Not sure if this indicated a lean pilot, or just the result of a super low idle.
In part I think the slides without the windows are more prone to this than the ones with. I have a #7 slide with no window.

I apologize to be coming to quote an old topic.

Jakobi, I'm very curious about this question I highlighted in its response. We reached a final conclusion?

 

[Jakobi]

I think it was just the low idle coupled with a lack of fuel pump/squirt jet on the PWK 2T carbs.

 

[Selvagem]

Thank Jakobi.

Jakobi, always believed that this little hesitation, by turning the throttle completely with the engine idling, was due to the idle circuit is poor. Would like an opinion, you set your carburetion at idle circuit based on this symptom? After reading countless your answers in several topics on carburetion, follow its recommendations and set my carburetion based on first leave the slide between 1mm and 2mm (currently this with 1.5mm) and the screw air at 1.5 turns. Adjusting this way the carburetor, I came to the following result:

PWK AS1 = Needle N3WE # 2
Pilot jet: 45
Main Jet: 175.
Air Screw: 1.5v

With this configuration, I can turn the throttle completely with the engine in motion Slow (very stable, by the way) that is not infirm hesitation.

Previously my setting was:

Needle: NECF # 3
Jet Pilot: 45
Main Jet: 175.
Air Screw: 1.5v.

With this setting, I have a hesitation, but the bike works very well. Not to happen hesitation, I need to use a Jet 48 pilot.

Jakobi, should I consider this little hesitation or I orient myself by other parameters?

Personally, I enjoyed the current configuration, with N3WE needle, I have a slight fat in small openings and the rest of the bike works clean, use this needle in the third position the carburetion is too rich.

Already grateful.

 

[Jakobi]

There is always a compromise.

When you tune the engine you are working with a range of variables from the carb settings (slide, needle, jets, float, etc) to the atmosphere (elevation, humidity, temp, etc) to the solid engine state (compression ratio, squish clearance, head design, port timing) and then the ignition timing on top.

Add to that the fuel requirements of the engine also change based on the load. A bike tuned to run cleanly in a trail setup which see's much low load part throttle and is chasing a smooth application will often be too lean for application on a motocross track where there are large loads and more aggressive throttle inputs.

As above, I feel that it comes down to the fact that there is no accelerator pump setup. On a 4T you have a squirt jet that supplies extra fuel when whacking the throttle open. It allows smooth delivery at part throttle and small inputs, but meets requirements when opening fast for a certain duration. With your 2T and PWK you need to compromise the balance. A bike setup that gives the best punch and response will feel rich in low load setups and may smoke or spooge more than usual. A clean running setup will lack the punch and response and feel smoother.

Find the balance that works for you and your application, while respecting signs of being too lean or rich such as poor idle (racing/flaming out), engine temps, how well the bike starts, how it performs in application.

All that said, I'm not an expert on the matter. Ideal AF ratio is ideal AF ratio, but that easily changes with the rest of the variables, so there must be some compromise somewhere.

 

[Selvagem]

Again thank you for sharing and helping their Jacobi knowledge.

Jacobi, I always try to find the balance you mentioned. But, there's something to this day I could not accept is as follows:

I particularly think my bike is with more fast idle than normal more easily than I would after submitting it to a stress situation, such as a rise in which we need to stop and start again in 1st gear with normal difficulties an intermediate level rider. In this example, the engine gets the most high idle, but in this instance, the engine temperature is far from a super heating or even begin to present the characteristic sound indicating very poor configuration ?Tan-Tan-Tan?

By reading and research I conducted, this symptom is caused by a needle with poor straight part and also a small Jet pilot and the practical test to prove this would leave the screw air 1.5v and being the hot engine and completely rotate idle speed the throttle, not shown infirm fails and the screw getting air in the range 1 to 2 turns, and the engine having an idle good, low circuit is OK.

On my bike, the float switch is perfectly set to 16mm, also proven by this practice informed way in this topic:

http://www.gasgasrider.org/forum/showthread.php?t=10173&highlight=float+set

Well, even with the current configuration that use, which uses a very rich needle, where it can completely turn the throttle without hesitation, my bike has the symptom that bothers me so much!

I watch the videos of Hard Enduro, KTM and listening to Jarvis and Walker is clear that they use rich settings, but do not perceive any spooge the exhaust and also I can not see changes in the engine operation even under high loads. Does this is due to the KTM engine be more tolerant of GasGas? Or maybe I'm being neurotic, looking for something that maybe in the future when the 2T have electronic fuel injection will be something of the past....

Sorry for the bad English.

 

[Jakobi]

I will say every ktm/husaberg/husky that I have had to dial in has been quick easy and effortless. They seem much less finicky than the Gassers. All of my engines have had the head machined (squish clearance reduced, angle matched to piston, compression ratio corrected). My cylinders get pulled and the transfers have any casting flaws cleaned up, and the exhaust spigot gets matched to the port. PV tension checked.

My first EC300 had a huge squish clearance and would not run consistently for the life of me.

Index your throttle to visually see which throttle areas you are working in. Sometimes heavy load can be above 1/2 throttle in a gear higher with low rpm. If you are lean in this throttle area it can still give the high idle once returned until the fuel catches up and cools things off again.

The more tinkering I do, the less neurotic I get. Chasing the last 10-20% of perfection always seems to introduce a counter issue. Seems to apply with engines and suspension alike.

 

[Selvagem]

Jakobi, again thank you.

My engine also had the Squish corrected, originally he had a gap of 2.4 mm and is currently 1.0mm.

The compression ratio I do not know calculate, but the mechanic who made this service to me informed me that the head of the volume went to 22ml.

The cylinder base've installed a board of 1.00 mm, and the ignition point set to 1.6mm BTDC.

After these adjustments made, my bike worked much better, cleaner and responding to small air screw settings, now 0.5 turns make much difference, which did not happen before.

Jacobi, I will follow your suggestion to score the throttle with reference points. Thinking about what you wrote, I really use higher speed and larger throttle openings, my way of pillotar is so. Maybe changing the main jet by a # 178 I can not eliminate this symptom that both annoys me? It really would be a great surprise to me as it will unlike anything I think.

Jacobi, what I clearly realized using the needle N3WE # 2, # 45 # 175 is that it binds more easily than with the needle NECF # 3, # 48, # 175 when the bike this hot. With the NE configuration, normally she calls the 2nd or 3rd kick and precise turn a little throttle, and the N3 setting each league in 1st Kick. In my opinion this indicates that the NE configuration is a bit rich.

Jacobi, please could better explain this part of your response, because I could not understand what you wanted to explain:

My cylinders get pulled and the transfers have any casting flaws cleaned up, and the exhaust spigot gets matched to the port. PV tension checked.

Thank you.

 

[Jakobi]

The part where the exhaust pipe mounts to the cylinder. I make sure they match each other. Usually there is some overlap.

I doubt this makes a noticeable difference in the grand scheme of things.