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


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  #1  
Old 05-19-2020, 01:37 AM
Delphinus Delphinus is offline
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Default EC300 Running Rich in first half of throttle

I have a 2007 EC300 with the AS1 (screw top) PWK 38 carb. It runs fantastic at full throttle, but not so great at low (0 to 1/2 throttle). Bogs down a bit before pulling away, and I've had a few examples where I've started it, it runs for a bit then dies and won't restart. Cleaning the plug usually means it starts for a bit then dies again. Putting in a new plug it starts up fine and stays running.
I assume this is rich.

Plug: BR8ES
Pilot: 40
Main: 175
Needle: N1EF
Needle Notch: 2 (from top)
Slide: *7
Mix: 50:1 with 95octane and Putoline MX7 (Was running Motul800 but have stopped).

I've checked float height, and that seems to be correct at 16-17mm. I'm at 140m (~500ft). Temps are 5-15C (41-60F) in New Zealand.
Looking through the jetting database, for this bike at these conditions most people seem to be running a richer setup, so I already seem leaner than normal.
I checked the reeds and they seem to be happy. Not letting anything other than a super tiny sliver of light in. A very small chip out of the corner of one of them (see attached).

If I wide open throttle it it usually runs a bit better, but most of my riding is slower technical singletrack. Is this something that I just have to deal with, or can I make it a bit crisper and responsive at the low end?
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File Type: jpg reeds1.jpg (26.4 KB, 5 views)


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Old 05-19-2020, 01:55 AM
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Jakobi Jakobi is offline
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Throw the needle in the rubbish. Get reading a few more threads.

N3EH wouldn't be a bad search term to get you started!
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Old 05-19-2020, 02:33 AM
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Gasser Nate Gasser Nate is offline
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I was going to say the same just about Jake! Throw a N3EG or H in there with a 40/42 pilot and a 175/178 main with a corrected float height and crack on.
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Old 05-19-2020, 03:24 AM
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In addition to the needle recommendation, IME, I've learned over time that on any PWK based carbs to run the float height at 18mm. It helps with overly rich conditions a lot of times.
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Old 05-19-2020, 03:58 AM
Delphinus Delphinus is offline
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Quote:
Originally Posted by Gasser Nate View Post
I was going to say the same just about Jake! Throw a N3EG or H in there with a 40/42 pilot and a 175/178 main with a corrected float height and crack on.
Do you mean run the N3EG with a 40 and 175, and the H with 42/178? Or any combination above?

Re float height, I did notice there is a dimple in the float tongue where the float valve sits in. Is this supposed to be there or has it worn in over time?
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Old 05-19-2020, 04:07 AM
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Those reeds won't be affecting the running yet but they won't be getting any better either. Lift them up and see if they are wearing as they hit the cage. Think I got mine from 454.co.nz. you could wet and dry them to keep them going for a few rides more but. .

Std needle needs a modification. Put it in the vice and give it just enough of a tweak that you won't be tempted to use it. A nail would be better.

Don't use a nail.
You might have joy from ktm shop or just online from aus.

Motul is a fantastic oil, that's not your problem but I bet a mate told you it was. Ahh, oil opinions.

Try a 42 and 175 as starting point, the needle will in combination with the pilot be leaner. Then try needle position and mix screw. Finally try if smaller main if you feel inclined.

Tip. Always think throttle position. Not rev range.

Just been riding my 07 last weekend . Still love it.
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Old 05-19-2020, 04:12 AM
Delphinus Delphinus is offline
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Quote:
Originally Posted by (F5) View Post
Those reeds won't be affecting the running yet but they won't be getting any better either.
Yeah have ordered a new set already, will pop them in next time I take things apart.

Lol @ nail! Definitely going to try a new needle next. Currently researching between N3EG or H (or I guess just get both?). What are you running in yours (as another NZ'er)?

If I leave the main jet alone, and just changing the needle, how badly can I break things by going too lean when changing needle?
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Old 05-19-2020, 06:26 AM
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Any jetting spec we throw up here will just be a starting point.

Both needles are the same profile. One is a touch leaner form closed to 1/8th throttle or there abouts - the area where it overlaps with the slide, pilot, and air screw.

A 175 main is likely ok. Given your cooler temps I'd go towards a 178 just because a little rich never hurt anyone. The needles suggested don't supply as much fuel towards WOT as the current N1EF.

Essentially you'll end up with similar top end mumbo, and a leaner more responsive engine at smaller throttle inputs.
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Old 05-19-2020, 02:08 PM
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My carb got a bit damaged by some grit that dropped in between the needle and tube (hello sticking throttle) so I replaced it with a KX tube block, I was on an N3 something which didn't work as well with kx tube.

I found a virtually new carb off a 17 which with a short adapter turned up ( shorter carb) and an RM needle is great.
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Old 05-19-2020, 07:57 PM
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I also live in the South Pacific worker Paradise (NZ)

02 EC300
40/42 pilot
N3EG needle. See below for Yamaha / KTM part numbers.
178 main
Attached Images
File Type: jpg 4SR-14916-EG-00.jpg (19.5 KB, 1 views)
File Type: jpg KTM N3EG.jpg (46.5 KB, 2 views)
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