Author Topic: 2021 300 SE Factory - Getting brand new bike jetted  (Read 965 times)

KTRacer14

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2021 300 SE Factory - Getting brand new bike jetted
« on: March 21, 2021, 01:30:46 AM »
2021 300SE Factory:  In general, how far off is the jetting chart in the manual...?   I set the bike up per the manual, and it seems very rich at 1/4 to 1/2 throttle.  As soon as you open the throttle, it starts 4-cycling.  Really absurd how rich the chart is.  It seems almost useless.  Just riding around my property, the plug looks too rich to go for a real ride.  I am afraid I will foul plugs right and left....

  • From what I can tell, the pilot jet needs to be about 1 leaner than the manual says.  So if it says run a 42...run a 40. 

  • Way too rich at mid throttle.  I will probably have to jump to what...a N8RG as I will run out of clip positions.  Two needle letters is equivalent to 1 clip position...right?

  • The main recommended does not seem terribly far off....maybe go one leaner. 

Is this at all consistent with what others have found?
« Last Edit: March 21, 2021, 01:54:56 AM by KTRacer14 »

Lv2RDST

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #1 on: March 21, 2021, 05:18:11 AM »
I'm following this as well. My 21 250se is on order. Is the picture attached the same you are looking at? And did you bike have the 40 pilot/165main from Sherco?

alang

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #2 on: March 21, 2021, 06:06:45 AM »
My 17 running
38 pilot
N8rh 2nd or 3rd
165mj
Air screw 1.5 out
Newer jetting seems way rich
2017 Sherco 300 2T Factory
2016 Aprilia Tuono 1100 Factory
2019 Santa Cruz Tallboy Carbon R
Azle, Texas

KTRacer14

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #3 on: March 22, 2021, 12:42:02 AM »
Lv2 - Yes....the bike came with the strange jetting set up...that is completely out of synch with the rest of settings on the chart.

40 Pilot
N8RE Needle
165 main

Look closely at the chart...there are actually only 10 different settings.  If you go diagonal down and right, the settings duplicate on the diagonal...except for the 25-36 Deg at 300-750m setting...which is just out of whack.

alang,

What temperature and altitude do you run that set up for?


alang

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #4 on: March 23, 2021, 05:58:01 PM »
50f to 90f
800 feet asl
Clip 3 when 50 to 70f
Clip 2 when 70f to 90f.
Of course. This is a 2017 300.
The last needle letter E is super rich.
« Last Edit: March 23, 2021, 05:59:36 PM by alang »
2017 Sherco 300 2T Factory
2016 Aprilia Tuono 1100 Factory
2019 Santa Cruz Tallboy Carbon R
Azle, Texas

DEL107

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #5 on: March 24, 2021, 03:19:41 PM »
Set your float bowl height for one. Mine was at 6mm, moved it to 7.5.

That helped mine run acceptable with the F needle that comes with the bike, and helped it respond to air screw tuning.

I found happiness using the popular KTM needle N3CH. 1/2 throttle is still a bit aggressive though so I'm be messing with other profiles, but at least it runs well.

My settings
38P
1.5 turns AS
N3CH #3
4600"
63F

remember, our bikes are different from earlier years, so expect different results if you're reading old threads and such
« Last Edit: March 24, 2021, 03:23:22 PM by DEL107 »

Sfade

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #6 on: March 26, 2021, 06:06:08 AM »
Before putting STIC block in I dropped one pilot size and dropped a JD red needle 3rd clip and I thought it was really good. By now you have 10 different answers.  Jetting is so subjective as to what "right" feels like.  The needle will make the most difference. 
2021 Sherco 300 SE Factory
2020 Sherco 300 SEF Factory (Supermoto)
2019 KTM 250XC

KTRacer14

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #7 on: March 28, 2021, 10:13:45 PM »
I think you must be right about the float bowl, because what I am seeing makes no sense at all.  I have always been told that jetting a PWK must be done in order:

1.  Pilot + Air Screw
2. Needle
3.  Main

You have to get the pilot right first before you can do anything else.

To tune the pilot, do the following:
1.  Put in your best guess as to which pilot is correct
2.  Warm the bike up.
3.  Set the Air Screw at 2
4.  Adjust the idle so the motor idles about 500 RPM higher than recommended.  So for a Sherco 300, set the idle to 2600 RPM.

Now play with the air screw.  You want to find the setting that produces the highest idle RPM.  If that occurs between 1 and 3 turns out on the air screw, you have the right pilot.  If below 1, your pilot is too lean (small).  If highest RPM occurs with the air screw more than 3 out, your pilot is too rich - go smaller.  Once you have the right pilot, you can tun the air screw for feel.  Usually it runs best about 1/2 to 3/4 richer than the "high RPM" setting.

I went though this, and got no good results.  The response to air screw tuning is not right.
4500 feet elevation
50 Def F
30% humidity

Started with 40 pilot. 
Warmed bike
Set RPM to 2600
Played with air screw.
Could not find a max RPM.  The more I leaned it out (air screw out more) the higher the RPM got.  RPM never peaked...all the way to 5 turns out....it just kept going up and and up.

So changed the pilot to a 38.  Same thing. No matter what I did...the air screw setting never gets "too lean".  The more I turn it out...the higher the RPM goes.  Also...even with a 38 pilot....the air screw has to be at least 1 out...or the bike will die. 

Must be a screwed up float bowl? Right?
« Last Edit: March 28, 2021, 10:27:24 PM by KTRacer14 »

erdat

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #8 on: April 14, 2021, 11:37:41 AM »
Hello KTRacer14,

PJ adjusting procedure is a bit diffrently explained then what you have. If you care to check it out below is the link.

https://www.cycleworld.com/story/bikes/kevin-cameron-explains-how-to-tune-carburetors/

by the why how were you able to read the RPM?

cheers,
erdat
'15 SE-R 250
Ankara, Turkey

KTRacer14

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #9 on: April 16, 2021, 01:50:47 PM »
erdat,

Thanks.  I reviewed that, and the initial adjustments from your link are exactly the same as my method. It says to start with the idle system (pilot). 

Quote
You will find a screw position that gives maximum engine idle speed such that turning the screws either in or out from that position causes engine rpm to decrease. This is the correct position. Think of it this way: The ideal air-fuel mixture makes the most horsepower at a given throttle setting—even at idle.

This is the problem, as I have already noted.  I am down to a 38 pilot, and no matter what I do...the more I turn out the air screw, the more idle rpm rises.  I get to 5+ turns out...and the idle just keeps going up.  So as it relates to my issue, your procedure is the same, and gives the same result.

I will play with the float bowl and see what I can figure out....

As for reading RPM...I installed an hour meter that has an RPM setting measurement mode.  I use that.  I also have a variety of electronic test equipment, including logic analyzers and oscilloscopes.  It does not take much circuitry (some wire wound around the spark plug wire, some filters and Schmidt triggers) to  create a square wave to measure RPM.
« Last Edit: April 16, 2021, 01:53:31 PM by KTRacer14 »

DEL107

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #10 on: April 16, 2021, 07:15:26 PM »
erdat,

Thanks.  I reviewed that, and the initial adjustments from your link are exactly the same as my method. It says to start with the idle system (pilot). 

Quote
You will find a screw position that gives maximum engine idle speed such that turning the screws either in or out from that position causes engine rpm to decrease. This is the correct position. Think of it this way: The ideal air-fuel mixture makes the most horsepower at a given throttle setting—even at idle.

This is the problem, as I have already noted.  I am down to a 38 pilot, and no matter what I do...the more I turn out the air screw, the more idle rpm rises.  I get to 5+ turns out...and the idle just keeps going up.  So as it relates to my issue, your procedure is the same, and gives the same result.

I will play with the float bowl and see what I can figure out....

As for reading RPM...I installed an hour meter that has an RPM setting measurement mode.  I use that.  I also have a variety of electronic test equipment, including logic analyzers and oscilloscopes.  It does not take much circuitry (some wire wound around the spark plug wire, some filters and Schmidt triggers) to  create a square wave to measure RPM.

Have you set your float yet? There are good videos on youtube for the keihin. Then source either a N8RH or a N3CH needle to cure the four stroking as you called it.

Have you even mentioned your temp and altitude? 

With a 38 pilot no way you should be out that far with the AS.It is actually ready to fall out at that many turns. Just set it at 1.5 with a corrected float and you shouldn't be more than +/- 1/4 turn from there. Personally I think you are using a bit high RPM for setting your AS, I'd stay down around 1600-1800. regular idle should be 1100 or so. I remember reading somewhere that too high of an idle bypasses the pilot circuit.

A JD kit is an option for good needles as well. I've just started to mess with the red needle a bit. @ 2400'/85F Red #4 was sublime, best I have ever felt it run. less spastic than the N3CH.


KTRacer14

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #11 on: April 18, 2021, 12:53:14 AM »
Recommended idle RPM per the manual is 2200 +/- 100.

Per my prior post.... prior testing was at:
4500 feet elevation
50 Def F
30% humidity

But the last few times I rode were at:
500 feet elevation
70 Def F
20% humidity

Probably similar air density.

I finally played with the float bowl.  It was at 7.4mm (mounted carb on a adjustable angle plate, and used a pop-off gage on the fuel line to get accurate readings).  That is right on the setting most have found to work.  But it clearly is NOT working right....so I raised it about 1mm...to 8.6.

I ran it and bike sounded a little less rich at idle, but it is still not acting right.

38 pilot.  Set AS at 2 turns out.  Set idle RPM at 2200 after warming bike up.  Then play with air screw:
1 Turn Out: 1800 RPM Idle
2 Turn Out: 2200 RPM Idle
3 Turn Out: 2500 RPM Idle
4 Turn Out: 2450 RPM Idle
5 Turn Out: 2480 RPM Idle

This is at least an improvement.  Before, the RPM kept on rising and rising.  The more I turned out the Air Screw, the higher the RPM went.  At least it stopped doing that!  Every carb is different.  Maybe this carb just wants a smaller pilot jet....  I guess I need to get a 35 pilot jet...  Really aggravating though...that the Sherco manual is so far off.  I mean it is not even in the right zip code....  What is the point of publishing recommendations that are so far off.
« Last Edit: April 18, 2021, 12:55:27 AM by KTRacer14 »

erdat

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #12 on: April 19, 2021, 03:27:24 AM »
I have been on this forum for quite some time now. Very good info on the website. I have learnt many useful info. So, thank you all that have and are contributing.
As far as I know, this treat is as far as the one of the most informative one on the carburetor settings as it relates to Sherco.
To sum up:
including the old ones and this one it seems that there is an overall consensus the the pilot size is a 38. But then KTRacer14 is reporting detailed info on his adjustment attempts. Interesting to see what's gonna turn out, may be a 35?
Bowl float level is set to high, needs dropping (I to did drop mine to 7.5mm).
H diameter needle (2.725)
clip position depending on the weather and altitude.

I do understand that is an overall generalization and as such needs to be cautiously regarded. I am sure that many of you know the below channel, here are two videos about his experiences on jetting

https://www.youtube.com/watch?v=7E4k5o-38m0&t=484s (at 2:16 he talks about jetting)

https://www.youtube.com/watch?v=idaeCNdORfU (here he tries a new needle, I believe his bike is a 250)

As DEL104 pointed out "I remember reading somewhere that too high of an idle bypasses the pilot circuit."

"This idle circuit delivers fuel only at or just above idle, and fades out as the throttle lifts because carb vacuum is no longer strong enough to lift fuel through this circuit." Ref: above link I provided under the section "Carburetor Systems"

but why would the rmp increase when the AS is turned out? Well one answer is obvious, the pJ is rich and there needs more air to burn it all, hence turning the AS skrew out results in a higher RMP.

But what if the slider is to high up, essential starting bypassing the pilot circuited, is that a possibility? perhaps the AS side is now supplying air to the main circuit?

From the same reference document I particular do not understand the part that is explained in the parentheses as it applies to PJ adjustment. My take was that the PJ adjustment needs to be done while the slide is completely shut. So only the PJ circuit is in use. This is the sentence that confuses me

Once the engine is warm you can set the idle speed (unless this is a racebike whose throttle slides close completely when the throttle is dropped). Idle speed is set by screw adjusters which slightly lift the throttles.

KTRacer14 I am really looking forward how the 35 PJ turns out?

Thanks you all again,
-Erdat


'15 SE-R 250
Ankara, Turkey

JL4049

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #13 on: April 19, 2021, 02:43:06 PM »
I'm a little surprised by the instruction to raise the idle speed slightly above normal to set the air screw. If your pilot jet is too rich, it'll require the slide to be lifted a fair bit (in relative terms) to get a fast idle. The problem with this is the carb will be starting to draw fuel through the main jet. When adjusting the airscrew, the method I use is to warm the bike up and back the idle down to slightly below normal before adjusting the airscrew until the highest rpm is reached. Then I'll drop the idle a little more, screw the airscrew in half a turn and do it again. If it peaks at the same point, I screw the airscrew in 1/8 turn from there and call it good. As others have said, if the final setting is more than 3 turns out you should put the next size down PJ in. If its less than 1 turn out, go up a size (you don't have to if you have found the sweet spot but it gives you a wider range of future adjustment to compensate for weather/altitude variations). My 2 cents YMMV

alang

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Re: 2021 300 SE Factory - Getting brand new bike jetted
« Reply #14 on: April 19, 2021, 06:07:55 PM »
Agree with others on setting
Air screw with idle speed low.
You want the idle circuit only.
2017 Sherco 300 2T Factory
2016 Aprilia Tuono 1100 Factory
2019 Santa Cruz Tallboy Carbon R
Azle, Texas