Upgrade to enjoy this feature!
Vital MX fantasy is free to play, but paid users have great benefits. Paid member benefits:
- View and download rider stats
- Pick trends
- Create a private league
- And more!
Only $10 for all 2024 SX, MX, and SMX series (regularly $30).
Today I rode the same track. Motoland MX park, AZ. 1400ft, 70-80 degrees. Here's where I started (when it was hotter) and where I am at now:
2021 Husq TC125
100LL Avgas, Maxima Super-M 40:1
Vented airbox cover
V-Force 4 reeds
Stock pipe/silencer---------------> Now Bill's pipe and MX2 Carbon silencer
Slide-5 (no notch on front)
Needle Jet S4
Needle 42-74-----------------------> Now 42-73
Clip-2--------------------------------->Now Clip-3
Pilot 35------------------------------->Now 37.5
Main 500----------------------------->Now 540
AS - 1-1/2 turns
Bike absolutely rips. No hint of a bog anywhere, no rich stumble or stutter, and zero drool. Additional note, I also changed to the 2016 and older KTM Domino throttle housing from G2 with G2's +20% quicker turn tube. I like the shorter throw much better than stock and I think it has the added benefit of making it easier to get the bike into the richer part of the needle and the main.
Specs:
S4 needle jet, 25 pilot jet, 42-75 top clip, 430 main, 80 starter jet, .75aso, full GJ mods, 7.5mm float level
Jd jet block and float needle gasket
Sea level
70f but 50-90f ohio weather.
Mostly single track and trail use
#4 slide with Reed side notch filed halfway to the one digger pictured a couple pages back. (Helped a lot... File more?)
Returns to idle great, no detonation, starts without choke, light smoke, no spooge, stock plug is pretty black after 10 hours (not sure if that matters)
Thanks for the help🤘
This should work pretty decent in Ohio. It's pretty similar to where I'm at now. Its the jetting currently in my bike and I've been running it for a few months now with no problems. It does smoke some when I first start it, but when everything gets to temp and out on track no more smoke.
Main jet 500
Pilot jet 32.5
Slide 5.75 (Kawasaki part#16025-0003)
Needle 43-75 (KTM part #55431134400)
Clip position #2
Needle jet S4 (KTM part #55431021400)
Air screw 1.5-2.0
55:1 fuel mix
Following this thread recommendation, I made some adjustments to the jetting for this weekend practice.
Needle pos 2 (from 3 stock)
Idle jet 32.5 (from 30 stock)
Main jet 490 (from 470 stock)
Airscrew 1.5 stock
Needle 42-71 stock
Needle Jet S4 stock
Slide #4 stock
Pump 91
The temperature was around 50f, maybe a bit colder in the morning. The track condition was really soft, a lot of sand going out of the corner.
The bike never had this power exiting corners before, was night and day difference. It was way faster rolling out of the corner too.
Looking forward to changing the slide for a #5 and JD gasket kit for peace of mind.
With the #5 slide do you guys think I will need to do small change to the rest of the setup or it's should be close?
Does the outside temperature affect allot the jetting on our bike? (95 % of our riding temperature out here is between 50f to 80f)
Thank you for making this thread, such a nice source of information for our Mikuni carb.
The Shop
With the temp swing if I need to adjust its normally 1 clip on the needle or a one size bigger pilot. Other than that its been just air screw adjustment to make sure I'm spot on and its pretty stable for temp swings.
According to the first post, the right needle for my setup with a #5 slide should be 42-74 right?
About modding my slide to a #5, any specials tips or tools I should know before getting into it?
How easy it is to mess up the slide completely?
Pit Row
Good idea on the throttle housing swap...I'll look into that as well.
Main Jet......Equivalent...........Fuel Flow (grams per minute)
400............none...................352
420............none...................372
440............none...................392
460............none...................410
480............none...................430
500............none...................453
520............none...................449
510N..........540.....................466
520N..........560.....................481
530N..........600.....................491
540N..........620.....................515
550N..........660.....................538
560N..........700.....................572
Size Comparison:
460 - .073
470 - .074
480 - .075
490 - Did not have one to check
500 - .078
520N - .079
540 - .077 (yes that's correct!)
560 - .079
sources:
dootalk
wheatfarm
I did not have to change jetting specifically for the Bill's system. same jetting I was running with the stock setup.
How about you? How are you doing with the jetting? Did you verify that your KTM came stock with the S-4? Did you try the 42-73 needle yet?
I'm pretty sure I miss-read the manual when I mentioned my bike came stock with a s-4 but I have not checked physically.
I do have the 42-73 needle to try and since the temps are finally cooling down. I'll test that out very soon.
Thanks for the info on the Bill's pipe/silencer. Just as I suspected, the stock exhaust is pretty good. When I had a 17' KTM 125, I installed an HGS exhaust which definitely added power on top but I could never get the jetting correct on that bike so it felt like an ON/OFF switch, and thus ,I don't really know how it affected the bottom or mid range. I can tell you the HGS pipe after the expansion chamber was a larger diameter than the 17' stock pipe so I was not surprised at the top end gain.
I believe there's power to be gained if you move from AvGas to T2 or T4. Stay away from the "e" versions of those fuels since those contain ethanol instead of MTBE.
Post a reply to: 125/150/250/300 KTM/HUS/GG jetting thread