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1/17/2017
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Rohnert Park, CA
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Fantasy
1803rd
As the title reads, my 2017 KTM 250SX apparently doesn't get along with the mikuni. Any experience in a better carb route? A litttle reluctant to try the Lectron, but have heard mostly positive reviews. Or is it more worthwhile to revert back to a 2016 Kehin carb? any insight would be greatly appreciated.
I did have the issue with the reeds and sanded the block so they would sit mostly flat. I think there was a small gap left from one reed being slightly conformed to the warped block.
I also adjusted float to recommended height (~8.5 - 9 mm I think).
Bike ran pretty good with 450 main, 35 pilot, stock needle, 3rd clip.
I then had 0.020" taken from cylinder head face and ran 430 main, 32.5 pilot, and stock needle 2nd clip. Had some very minor pinging at a particular rpm/throttle position.
Before yesterday's ride, I installed the JD Jet kit blue needle on 4th clip, along with a 30 pilot jet and AS at ~2.5 turns out, and now it runs better than ever. I was very skeptical of the JD Jetting kit, but it is actually better. Maybe not $70 better, but over the life of the bike it's probably worth it. BTW, I'm running 93 octane at 32:1.
So, since you've checked your reeds I would start by checking float. And then adjust pilot, needle, and main to get the performance you're looking for.
What jetting are you currently running?
The Shop
I have toyed around with the jetting a bit, until I finally became fairly happy with it, but honestly, I've felt like there is just a lot of locked potential, especially up top.
What Carb did you go with? 2016 SX Kehin? And what needed to be modified if anything?
leaner pilot jet
richer main jet
Vforce 4R
Bud/HGS exhaust
power valve spring backed out (not quite flush with case)
Bike is running like a monster
Down low is phenomenal. Up top seems weak to me.
I started off with the jetting that I had in my 2015 250sx but it was way too lean in the 17 TC250. The new bike really wants quite a bit of fuel in comparison. In my 2015 I was running 158 main, 38 pilot, and NECJ suzuki needle. On my 17 I am running 168 main, 42 pilot with NECJ needle still. I am at about 5000' and it is just about perfect.
I am also running the Vforce 4R reed cage. Tried drilling the airbox that everyone claims to fix everything, but I did not notice any change at all other than air filters getting dirtier way faster.
As far as I know KTM does not offer a #6 slide for the Mikuni. Honda sell's a 5.75 slide, as does Kaw also, through the 04 cr125, which is a little cheaper, but I'm not sure of it's availability
Pit Row
Still running the JD Jet Kit on blue needle, 4th clip. Changed pilot to 27.5 for the summer. Main still a 420 or 430 (can't remember now).
With the head mod I'm still able to run pump gas and leaner jetting without any issue. Has been very stable from 60 deg. Fahr up to 100+ deg. Fahr. and only required minor changes.
With the JD needle, a much leaner pilot is required (came with a 32.5). With the stock needle, somewhere in the 35 to 40 range would probably work for most.
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