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Out of curiosity I just measured the "stock" setting on my TC125 and it is 3.5 turns in from all the way out. I'll try the recommended 1.75 in this thread and see what the change is.
The Shop
Today I rode the same track. Motoland MX park, AZ. 1400ft, 80-90 degrees. Here's where I started (when it was hotter), then when it was 70-80, 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)(no notch is not actually true, the 5.0 slide comes with a very small notch in it)
Needle Jet S4
Needle 42-74-----------------------> Now 42-73------------------------------> Back to 42-74
Clip-2--------------------------------->Now Clip-3-------------------------------> still clip 3 with the 42-74
Pilot 35------------------------------->Now 37.5
Main 500----------------------------->Now 540
AS - 1-1/2 turns-------------------------------------------------------------------> Now 1.75
PV - 3.5 turns in-------------------------------------------------------------------> now 2.25 turns in, more info below.
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.
4/5/2021 PV update. We had some previous discussion about PV preload setting. I tried going to AJ's 1.75 turns setting. As expected, the bike became lazy on the bottom and required dropping to 2nd more and more clutch abuse in corners. I then tried 2.75 and this was too snappy and touchy. Was lighting the tire up on shiny spots and the power would spool up too quick and then fall flat, many times peaking too early for the next jump. I could see this being great on a really tight track or in the woods maybe. So, I split the difference and went to 2.25 and now it's really nice. Comes on just quick enough and strong enough but is smooth and steady. At the end of the day, it seems both jetting and PV preload affect the response of the bike in different, but complimentary ways. So you have to balance the 2.
** Thinking more about it... if you went from 3.5 to 2.25 that's 1.25 turns which from the mag article they mentioned what a 150rpm swing per 1 turn at 5600rpms so ~187rpm swing from the stock jetting to your happy spot.
As for the tool, the shank on a Craftsman screwdriver just happens to be the right size. I've noticed some of the tools you can buy are actually pretty cheap too.
I have a 2019 KTM 150sx. I am running the suggested jetting from the first page. Maxima Super M mixed 40:1 with VP110. 5.0 slide is notched as well. The bike rips when out on the track and no complaints but I'm having some starting issues which is very frustrating.
Ive dropped from a 30 to a 25 pilot and the bike still struggles to start when i sit for 20-30 minutes in-between motos, and its not first or second kick when cold either. Ive even wet fouled some plugs. Seems my problem occurs when I'm done doing a moto and lug back to the truck. Once i get the bike running i need to clear it out for sure but after that its good to go.
Checked the reeds, theyre good, top end has less than 20 hours on it and kicker has good compression by feel. Everything leads me to think i need to drop to 22.5 but thats seems pretty far off from whats recommended.... I haven't set the air screw properly but its definitely over 3 turns out just messing with it to get the bike started. The past couple times I've ridden its been 70-80 degrees in the Pittsburgh Pa area so ~1000' elevation
Have you updated the jet block gasket?
Pit Row
Next, enlarging the notch on the front of the slide increases the draw on the pilot as Digger has said many times. I personally have not enlarged the notch and am running a 37.5 (on a 125) and it's great. Can you post a pic and dimensions of the enlarged notch on your slide?
I want to check my needle valve and float height again today. Maybe it’s bleeding through and flooding the engine. Noticed after cleaning the bike yesterday that when I lift and lean it over onto the stand I was overflowing gas with the hose looped
Air screw is only a turn out with the above symptoms, same temps/elevation/jetting as Page 1 and I did manage to get a 5.75 slide in the end.
This is on a 250sx, any suggestions, any answers appreciated, thanks again folks.
I set the float height (or rather didn't set it, it was actually correct as it was weirdly) and replaced the jet block gasket while I was in there.
I have made the following modifications:
1) V-Force 4 reed block
2) FMF Factory Fatty pipe
3) FMF Powercore 2.1 silencer
4) Renegade SX2 race fuel mixed with Maxima 927 at 32:1
I live in the southeast and ride at an elevation between 600'-1200'. Can someone give me a starting point for jetting please? I would prefer it to be just a shade on the lean side.
Thanks in advance!
Sure someone will chime in with a proper answer soon. And hopefully to my post above yours too, air screw didn't cut it, just about to kick it over with a 35 pilot.
Octane – R+M/2 104.5
Motor Octane 100
Research Octane 109
Specific Gravity 0.717
RVP 8.35
Oxygen 5.6%
Leaded Yes
Based on the specs, I would say it's pretty close to the AvGas I run (low'ish spec gravity) and then with O2 content added. Take a look at my specs a few posts back. They are basically the original specs from this thread with a little bit of richening up to account for the low spec gravity. The O2 content of your fuel is going to lean it out a bit from there.
Post a reply to: 125/150/250/300 KTM/HUS/GG jetting thread