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Ktm 300 jetting issue

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ImageUploadedByThumper Talk1467296627.467890.jpg. This is what is like after riding very short in 2nd gear below half throtle. And when i pull he. Throtle same problem. Could it be the float level? Edited by avliviu

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Use the "whack the throttle" method to tune the air screw. It's easiest way to tune the carb to get clean, no hesitation response off idle.

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Piston says to me:

 

Black carbon in the middle and the no carbon tobacco brown in front of the trasfer ports

1. main jet rich  ( and or main thottle position where you ride all the time is rich

2.  tobacco brown usually means you have a lean spot your are going past all the time as you open and close throttle

3. the no black carbon area is piston wash from incoming fuel mixture, wash usually caused by raw fuel entering combustion chamber, on a carb engine  about 8mm wide little  thumb nail size wash spot would be ideal

 

Problem with ideal is you have a Keihin carb and there is no perfect on them, only a fair compromise at best. My pal with 2015  300 fought his jetting daily for a year, while I watched and  offered an obvious solution.   Then he bought a smart carb,  way way better, but far from real good.    After pipes, heads, different ignition, gearing changes a $600 carb, we installed a Lectron carb, Makes you want to cry. $2000 worth of jets/pipes/ignition/reeds etc etc.....all a waste   In a day of riding and tuning  the Lectron send for the 300,super nice running bike.  All three rejected pipes work great now, just different power delivery.   Good steady top to bottom fuel delivery is hard to achieve, that why the companies are quickly going to FI.  

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So i am still dealing with the richness problem even with the smaller jets and necj needle. today i managed to make a test with a friend;s number 6 slide.

the slide was moded.in the place where the needle sits it was drilled a hole to let the needle be lower. i put the n2zj needle and surprise: the bike run very good. it was lowered about 2,5 more clips .

so ..is there a needle so lean after n2zj ? 

thanks

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So i am still dealing with the richness problem even with the smaller jets and necj needle. today i managed to make a test with a friend;s number 6 slide.

the slide was moded.in the place where the needle sits it was drilled a hole to let the needle be lower. i put the n2zj needle and surprise: the bike run very good. it was lowered about 2,5 more clips .

so ..is there a needle so lean after n2zj ?

thanks

What clip position did you run the NECJ in

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in the 1st clip. started with 2nd

1st clip should have been lean as especially with such a small pilot , did you drop the main size down at least 2 sizes with the NECJ needle ?

If it's that rich down low with a small pilot and lean needle settings you sure your reeds are in good nick ?

What baffles me is the NECJ is about 1.5clip positions LEANER then the n2zj ....but the NECJ is running richer ?

Edited by kxrob

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Also to answer your question about leaner needles

Here's a list

Leaner to richer

N3cj (dual taper) NECJ (triple taper)

NEDJ (triple taper )

N8rj (dual taper)

N2zj (dual taper)

N8rw (dual taper )

N2zw ( dual taper)

N8rh (dual taper)

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Needle From 1/4-3/4

Pilot 0-1/4

N2xx , n8xx , n3xx are leaner at 3/4 to WOT transition, this is why you need a richer main then with the NExx needles

4th letter is 1st taper diameter

3rd letter is clip position xxCx is leaner then xxZx needle in same clip positions

Edited by kxrob

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looks good to me 

was that a WOT pull ?

or 1/2 throttle ?

what were your settings ?

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WOT for about 8 seconds. 38 pilot 168 main. n2zj. i moded the slide so that the needle would drop off more. about 2 mm. i think the needle jet is worne and that s why it mut go down more.

Edited by avliviu

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with the slide mod you did i think what you emulated was the needle being down so far is turned a rich needle (n2zj) into a leaner necj in about the second position

 

if you run a n2zj in clip 2 it as rich as a necj in clip 3.5

 

so by my calculations a modified slide to sit a n2zj 2 mm lower should have run exactly the same as a necj in clip 1

(there is about 1mm between clip positions on needle)

 

romania is similar altitude and temp as australia at the moment and if i run the same settings as you i would melt a piston

 

please make sure your testing is correct , (do a plug chop with a fresh plug at 14-12 throttle to check the needle for leaness

 

your test above is only for the main and looks good and safe to me a 165 would work also

just remember tho if you switch back to the NECJ needle then your main will be to rich

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please make sure your testing is correct , (do a plug chop with a fresh plug at 14-12 throttle to check the needle for leaness

Please explain this. I m not fammiliar with all the tehnical words in english.

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Sorry , between 1/4and 1/2 throttle and kill engine the same way you did your full throttle run to test your main

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