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Enduro Intake/Carburetion - 2 stroke Jetting, Reeds, Air Filters, etc.


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Old 08-05-2019, 04:10 PM
Jinx_pt Jinx_pt is offline
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Default Spark plug color good, bad or what?!!

Hi guys!!

2013 gasgas 300R
AS2 carburetor
Needle & notch =NECW #2
Main jet = 172
Pilot jet = 42
Air screw setting = 2 1/2
Throttle valve:7
Fuel: 98oct
Oil:MOTOREX CROSS POWER 2T at 1.5%
Elevation: Sea level to 500m
Temp C?: Summer 20 to 35/ Winter 0 to 15


Been trying to get the best result without changing a lot.
Most likely i should put a 40 PJ, but maybe i can manage with the 42PJ since i dont ride a lot with hot weather....

I have been using mostly 95oct... but decided to try 98oct on the last couple rides with a new spark plug.
Before with 95oct plug was all black but now, spark plug color is a dark brown, (i upload image) and porcelain is gray. I know that dark brown is a better color, but what about that gray porcelain?!?!

Im still learning about jetting, so better to ask...
P_20190804_184715.jpg

Any thoughts on this will be appreciate!!



Last edited by Jinx_pt; 08-06-2019 at 02:38 PM.
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Old 08-05-2019, 06:03 PM
Jacob 'Berg Jacob 'Berg is offline
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Location: Scottsdale, AZ
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Quote:
Originally Posted by Jinx_pt View Post
Hi guys!!

AS2 carburetor
Needle & notch =NECW #2
Main jet = 172
Pilot jet = 42
Air screw setting = 2 1/2
Throttle valve:7
Fuel: 98oct
Oil:MOTOREX CROSS POWER 2T at 1.5%
Elevation: Sea level to 500m
Temp C?: Summer 20 to 35/ Winter 0 to 15


Been trying to get the best result without changing a lot.
Most likely i should put a 40 PJ, but maybe i can manage with the 42PJ since i dont ride a lot with hot weather....

I have been using mostly 95oct... but decided to try 98oct on the last couple rides with a new spark plug.
Before with 95oct plug was all black but now, spark plug color is a dark brown, (i upload image) and porcelain is gray. I know that dark brown is a better color, but what about that gray porcelain?!?!

Im still learning about jetting, so better to ask...
Attachment 8348

Any thoughts on this will be appreciate!!
What bike year and displacement?
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Old 08-05-2019, 06:59 PM
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barossi73 barossi73 is offline
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Plug readings are hit and miss,if you tool around trials like and pull plug it will look quite different to a wot hot run plug.Try it...the plug indicates relative to how you were last riding.
That said,assuming thats a fair indicator of your typical riding it looks ok,leanish maybe,the NEDW#2 would be 1/2 clip richer= NECW#2.5
Most important is how it feels at different throttle
Also 1.5% oil ratio seems light to me
I would give NEDW#2 a try first,half a clip can be significant.
Disclaimer...there are far more knowledgeable jetters on this forum by miles than me lol if im lucky one of them will agree with me
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Old 08-06-2019, 12:57 AM
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SS109 SS109 is offline
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Here's the jetting guide I follow (from KDXrider.net). It has worked great for me jetting any brand of bike.

Quote:
A correctly jetted carb makes a tremendous difference in the torque, mid range pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's powerband. A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using. A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift. Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting.

The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent. Unless the person telling you what jets to use is riding an identical bike, on the exact same track, at the same time, his recommendations are meaningless. Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best.

Before you start to jet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel. One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Worn reeds will mimic rich jetting, and worn rings will mimic lean jetting. Install a fresh plug. Set the float level to the proper specs, an incorrect float height will affect your jetting all across the throttle range. Warm the bike completely, and shut it off.

It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving. Turn the airscrew all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idling. Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the airscrew for the best response.

Now is the time to determine if you have the correct pilot installed in your carb. The airscrew position determines this for you, making it very simple. If your airscrew is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet. Once you have determined (and installed it if it's necessary to change it) the correct pilot jet size, and tuned the airscrew for the fastest idle, it's time to tune the airscrew for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the airscrew slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn. The airscrew is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the airscrew to compensate for changing outdoor temps and humidity. An airscrew setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day.

Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.

Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan.

Once you have a little bit of experience with jetting changes, and you start to learn the difference in feel between "rich" and "lean", you'll begin to learn, just from the sound of the exhaust and the feel of the power, not only if the bike is running rich or lean, but even which one of the carb circuits is the culprit. The slide is also a tuning variable for jetting, but slides are very expensive, and few bikes need different slides, so we won't go into that here.
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Old 08-06-2019, 02:37 PM
Jinx_pt Jinx_pt is offline
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Quote:
Originally Posted by Jacob 'Berg View Post
What bike year and displacement?
Sorry, i forgot..... going to edit post!
It?s a 2013 gasgas 300R

Quote:
Originally Posted by barossi73 View Post
Plug readings are hit and miss,if you tool around trials like and pull plug it will look quite different to a wot hot run plug.Try it...the plug indicates relative to how you were last riding.
That said,assuming thats a fair indicator of your typical riding it looks ok,leanish maybe,the NEDW#2 would be 1/2 clip richer= NECW#2.5
Most important is how it feels at different throttle
Also 1.5% oil ratio seems light to me
I would give NEDW#2 a try first,half a clip can be significant.
Disclaimer...there are far more knowledgeable jetters on this forum by miles than me lol if im lucky one of them will agree with me
I was just wondering if that gray color was normal, since brown is everywere. Maybe that was an indication of some problem or not! SO better to ask right?!! Gonna try to get better adjustment of the jetting.

Me and lost of friends use 1.5% oil ratio for years and no problems. Im almost with 100hours in this piston and ZERO problems. We dont stay a lot of time WOT... we ride in a hard enduro terrain, so its pretty much 2?/3? gear all the time!


Thank you all for the replay!!
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