2020 Husky TC125 jetting ?

braaap707
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braaap707
Edited Date/Time 2/19/2022 3:51am
Hi everyone I know this has come up few times with others before and want some opinons. So have about 11 hours on the bike. So far it's been great bike but jetting has been a headache. Currently at a 30 pilot and I have no more position on the needle. Seems wrong to have to go even smaller ? I did go from a 450 to a 460 cause I was running out of top pull so mid and up runs great. Down low isn't. Has a hesatstion till it gets into the mid. If i can't get it sorted a lectron or keihn is gonna go on but I want to make this thing work at least for time being. Only mods are pc 304r shorty and Vforce 4 reed cage. I run vp 110 or vpr mixed at 40 to 1 with maxima super m. Live in New England. Overall just kinda fustrsting cause my 16 tc125, similar motor with a keihn, that was totally stock aside from fmf silencer absouelty ripped and I jetted it once and rode it all year.
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Kyle978
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Kyle978 6/28/2020 11:01am
6/28/2020 11:01am
Just hold her wide
cbeez243
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cbeez243 6/28/2020 11:33am
6/28/2020 11:33am
42-71 needle second clip, 470 main 32.5 or 35 pilot, 1.5 air screw
AgileMike
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AgileMike 6/28/2020 3:09pm
6/28/2020 3:09pm
It sucks to hear on a new bike, but just put a Lectron on it and be done. You will thank me after 50- 100 hours of near perfect jetting
4
piscokid
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piscokid 6/28/2020 7:25pm
6/28/2020 7:25pm Edited Date/Time 6/28/2020 7:31pm
KTM 125 JETTING

From vital member digger who helped me fix our jetting:


1) S-4---needle jet---KTM Part# 55431021400 ( it goes underneath the main jet holder )

2) a 42-75 needle in the 3rd clip position http://www.motosport.com/oem-parts/part-number/284-14116-H5-00?mmysourc…

3) #5 slide----you can either have you current slide cut--http://www.rb-designs.com/rb_designs_llc_013.htm or you can buy one---http://www.motosport.com/oem-parts/part-number/16025-0002?mmysource=kaw…

4) a 37.5 pilot jet

5) 480 main

6) set the air screw at 1.75 turns out, to start out with.

This really needs to be done as a unit. The S-4 needle jet requires the leaner slide and leaner needle to bring everything together.


Here is another thing to check: The little gasket under the jet block. They have a tendency to deform and cause the low end issues you describe.

https://jdjetting.com/product/jdmk05-mikuni-tmx-jet-block-kit/

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digger
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digger 6/28/2020 8:51pm
6/28/2020 8:51pm
piscokid wrote:
KTM 125 JETTING From vital member digger who helped me fix our jetting: 1) S-4---needle jet---KTM Part# 55431021400 ( it goes underneath the main jet holder...
KTM 125 JETTING

From vital member digger who helped me fix our jetting:


1) S-4---needle jet---KTM Part# 55431021400 ( it goes underneath the main jet holder )

2) a 42-75 needle in the 3rd clip position http://www.motosport.com/oem-parts/part-number/284-14116-H5-00?mmysourc…

3) #5 slide----you can either have you current slide cut--http://www.rb-designs.com/rb_designs_llc_013.htm or you can buy one---http://www.motosport.com/oem-parts/part-number/16025-0002?mmysource=kaw…

4) a 37.5 pilot jet

5) 480 main

6) set the air screw at 1.75 turns out, to start out with.

This really needs to be done as a unit. The S-4 needle jet requires the leaner slide and leaner needle to bring everything together.


Here is another thing to check: The little gasket under the jet block. They have a tendency to deform and cause the low end issues you describe.

https://jdjetting.com/product/jdmk05-mikuni-tmx-jet-block-kit/

1--Replace the jet block gasket

2--42-74 needle in the 2nd clip position.

3--#5 slide, I like to notch(4mm wide x 4mm deep) them on the front side, as it makes the pilot circuit more efficient, which in turn helps the bike idle better. This often times causes the need to run a leaner pilot jet.

4--35 pilot for an un-notched slide, and a 32.5 with a notched slide.

5--490 main

6--set the air screw a at 1.5 turns out from fully closed.

I believe your 20' sx125 comes with the s-4 already in it.

these are just starting #'s for sea level to 2500' and normal summer time temps, 60-85, that will get you in the ballpark, but you may need to play with the pilot and air screw a little.
6
Alex.434
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Alex.434 6/28/2020 11:32pm
6/28/2020 11:32pm
AgileMike wrote:
It sucks to hear on a new bike, but just put a Lectron on it and be done. You will thank me after 50- 100 hours...
It sucks to hear on a new bike, but just put a Lectron on it and be done. You will thank me after 50- 100 hours of near perfect jetting
This is what I did on my 2017 TC250. Took the OEM carb and throttle setup off Day 1 and sold it for almost half the cost of a Lectron.

I had a couple teething problems as I was one of the first guys to get a new-gen TC/SX platform with a Lectron, so the setting had to get dialed in with the guys a bit, but once we got it sorted it's been fantastic.
Deja New
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Deja New 6/29/2020 4:35am
6/29/2020 4:35am
I have a TC250 that can do no wrong just does a TC85 that is the same also aTC50 it goes and goes but my TC125 just bogs drooped it of at the local mechanic hope he can sort it .
BikePilot
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BikePilot 6/29/2020 5:16am
6/29/2020 5:16am
Making the side notch bigger improves throttle response at low throttle openings. Also don’t forget to drill out the main jet cup and baffle so it doesn’t starve for fuel on top.
HighPlainsSquid 6/29/2020 6:51am
6/29/2020 6:51am
Have you opened up the side panels to get some air to the airbox? That's still a "thing" on the 2020, right?

My '15 runs GREAT but I have a Keihin on it. Both of our KTM 150's have Lectrons. Mikuni on the shelf, but the list of advice given above is very close to where I was with the Mik on the 150's.
piscokid
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piscokid 6/29/2020 10:11am
6/29/2020 10:11am
Listen to DIGGER. That dude is the MAN!
endurox
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endurox 6/29/2020 10:39am
6/29/2020 10:39am
Cut the slide to a 6.5mm 32.5 pilot jd red needle and 450 main. This works at 3-7k feet. Also replace block jet gasket with JD gasket.
Spudnut
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Spudnut 6/29/2020 11:00am
6/29/2020 11:00am
Mix it to what the book calls for with the recommended oil. I believe the 125s are 50:1? You will have to check though
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braaap707
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braaap707 6/30/2020 4:46pm
6/30/2020 4:46pm Edited Date/Time 6/30/2020 4:46pm
Thanks for the input everyone. Gonna try knotching the slide and replacing the jet block gasket as digger suggested. Hoping it'll be a noticeable improvment. Decided to get one of the optional 2020 4 stroke vented airbox covers as well so I'll have that to play with too. I'll post up with what I get for results this weekend.
MxKing809
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MxKing809 6/30/2020 5:27pm
6/30/2020 5:27pm Edited Date/Time 6/30/2020 5:29pm
It’s been 85-90 Degrees here in Michigan and I’m on a 150... but here is mine:

43 needle (stock was 42-71) in the second clip
Dropped pilot down to 30 from 32
470 main (might try a 480 to see if it’ll pull it)
Air screw 1.5 out

Mine was fat as hell on the bottom. I’m running 50/50 93 and 110 sonoco gas, and 40:1 Motorex premix. We’re about 600’ above sea level with 90-100% humidity.


This cleaned mine up big time! The hesitation and blubber on the bottom is gone.
AJ565
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AJ565 6/30/2020 7:16pm
6/30/2020 7:16pm
braaap707 wrote:
Thanks for the input everyone. Gonna try knotching the slide and replacing the jet block gasket as digger suggested. Hoping it'll be a noticeable improvment. Decided...
Thanks for the input everyone. Gonna try knotching the slide and replacing the jet block gasket as digger suggested. Hoping it'll be a noticeable improvment. Decided to get one of the optional 2020 4 stroke vented airbox covers as well so I'll have that to play with too. I'll post up with what I get for results this weekend.
For sure listen to digger, he’s the one that got us on the right path with the 250’s a few years ago.
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Teemu
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Teemu 7/1/2020 2:27am
7/1/2020 2:27am
You can also try the "sand" setting from manual. If I can remember right 42-71 needle (3 clip from top), 37,5 and 580 jets. Air screw 2 turns open. I have find out that is working the best in every track. I have been running it with 98 and 101 euro fuel.
digger
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digger 7/1/2020 7:20pm
7/1/2020 7:20pm
I checked my notes on the 19’ TC 125 that I worked on last summer. The stock needle jet was a richer S-7 and not the S-4 That the Mikuni needs.
The setup I listed above is pretty much, do all of the above or don’t bother. You cannot half ass it by trying to piece it together one component at a time. After looking at my notes I ended up with a 27.5 pilot
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Ray Knight
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Ray Knight 7/1/2020 8:00pm
7/1/2020 8:00pm
I got that Mikuni working awesome on my 250sx and YZ125 but tried everything to no avail on my TC125 and 150XCW. I ended up swapping to the JD Kehin carb on the TC125 (works amazing crisp and clean) and the Lectron on my 150 which also works perfect but i think the Kehin is a better fit for the 125. The Lectron makes less of a hit and more torque feel. Great for offroad. The Kehin has a more free revving feel and i like it on my 125.

Other mods that i really like on the TC125 are the RK Tech head, Vforce 4, F1 moto PV arms, Red PV spring and i tried the FMF fatty and PC pipe and liked the midrange hit on the PC pipe best.




Indy mxer
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Indy mxer 7/2/2020 5:04am
7/2/2020 5:04am
I put a JD jet kit in my 15 TC125 and it cleaned it right up. Runs crisp. I've always had good luck with JD over the years.
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AJ565
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AJ565 7/2/2020 6:08am
7/2/2020 6:08am
Indy mxer wrote:
I put a JD jet kit in my 15 TC125 and it cleaned it right up. Runs crisp. I've always had good luck with JD over...
I put a JD jet kit in my 15 TC125 and it cleaned it right up. Runs crisp. I've always had good luck with JD over the years.
Different carb and it doesn't work that well in the 16+ bikes.
piscokid
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piscokid 7/2/2020 6:35am
7/2/2020 6:35am
digger wrote:
I checked my notes on the 19’ TC 125 that I worked on last summer. The stock needle jet was a richer S-7 and not the...
I checked my notes on the 19’ TC 125 that I worked on last summer. The stock needle jet was a richer S-7 and not the S-4 That the Mikuni needs.
The setup I listed above is pretty much, do all of the above or don’t bother. You cannot half ass it by trying to piece it together one component at a time. After looking at my notes I ended up with a 27.5 pilot
He speaks the truth. Do it all. The damn thing runs so good and sounds so different than the other KTM/Husky 125's. I have people asking all the time what we have done to the bike. It has an FMF pipe and silencer and is super crisp. Plug is perfect brownish tan. 93 pump gas with a dash of Klotz octane boost and Maxima 927 at 40-1.
Indy mxer
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Indy mxer 7/2/2020 10:05am
7/2/2020 10:05am
Indy mxer wrote:
I put a JD jet kit in my 15 TC125 and it cleaned it right up. Runs crisp. I've always had good luck with JD over...
I put a JD jet kit in my 15 TC125 and it cleaned it right up. Runs crisp. I've always had good luck with JD over the years.
AJ565 wrote:
Different carb and it doesn't work that well in the 16+ bikes.
I bought a nice 2016 SX125 last year and put a JD jet kit in it. Also a new FMF pipe and silencer. It was really crisp as well.
But my oldest son is a longtime motorcycle tech and did the jetting for me. I had no complaints. Sold it last fall and the guy that bought it thought it ran very well. But it does seem that the Husky and KTM 125's can be hard to get right.
braaap707
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braaap707 7/2/2020 5:16pm
7/2/2020 5:16pm
All good feedback guys. Appreciate it ! So did what u suggested digger and got all his above mentioned mods as well. Ordered a set of the f1 powervalve arms too. Evetually ill maybe do vhm or similar head. Also snagged a keihn 38mm from a 99 380 sx a friend at work today. Pretty sure its a Airstryker not a older style pj ? Havent even looked at it close enough to make sure. Does have separate choke knob and idle screw so thought thats a identifying part between the 2. Side note, rode his 380 with the lectron and was thoroughly impressed but for 500 bucks ill stick with what i have. I will test the mikuni with the noted mods back to back with the keihn I just got and I'll post up with how I feel about both setups. Now just need this damn rain to stop so won't everything won't be a slop pit.
braaap707
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braaap707 7/5/2020 8:06am
7/5/2020 8:06am
So here's my update guys. Did all the above mentioned mods except for the 27.5 pilot. Thought I grabbed one and actually grabbed a 30 which is what in it have. Dohh. Knotched the slide per diggers specs, S4 needle jet was already in it. Replaced jet block gasket, #5 slide was used, bike seemed to like a 480 main not a 490 which was little blubbery up top but 480 helped it pull better then the 460 I had in. Overall it was all a huge improvment. However I wasn't perfectly happy with it's mid to top transition. Just isn't perfect like my 16's keihn. So I threw the keihn on. Was damn good right from start. Bumped pilot from 45 to 40 and it's the perfect feel I've been looking for. Still not gonna completely give up on the mikuni, still waiting on 42-74 needle and need to grab a 27.5 pilot from work but for now keihn will stay on. In a weird happenstance, my 96 cr250 has been acting funny and discovered it's keihn had a crappy slide, chipped plating. Threw the huskys mikuni on it and bam ! Thing runs actually awesome with the mikuni and it's current setup ! Lol I'll throw up some pics later and some more ride reports mid week when I get those other mikuni parts and I'll try the mikuni one last time on the husky. If i decide its the keihn im going with think ill throw some money and buy a newer air striker and maybe a STIC metering block.
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bluemotocross 2/19/2022 3:51am
2/19/2022 3:51am
digger wrote:
I checked my notes on the 19’ TC 125 that I worked on last summer. The stock needle jet was a richer S-7 and not the...
I checked my notes on the 19’ TC 125 that I worked on last summer. The stock needle jet was a richer S-7 and not the S-4 That the Mikuni needs.
The setup I listed above is pretty much, do all of the above or don’t bother. You cannot half ass it by trying to piece it together one component at a time. After looking at my notes I ended up with a 27.5 pilot
hi digger,i realize this is an old post,and thank you for getting me and lots of others on the right track with our 125/150's..once i changed my slide,and shared it with the others on ktm 125/150 fb group,many of us are reaping the benefits of your work..i joined the site mainly to comment on this post..i think if you look into it,you'll find the needle jet is S-1,not 7..i got a big old magnifying glass i use to read them,. i will be pulling my jet in the next couple days to see if my 18 tc125,with a ktm 150 kit,came stock with S-1 or S-4..to get to the point,i think you saw a 7,where it is actually a 1..the only two options are s-4 and s-1..if i'm right,you can update your notes..if i'm wrong,please let me know...thanks again bud..
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digger
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digger 1/10/2025 7:05am
1/10/2025 7:05am
bluemotocross wrote:
hi digger,i realize this is an old post,and thank you for getting me and lots of others on the right track with our 125/150's..once i changed...
hi digger,i realize this is an old post,and thank you for getting me and lots of others on the right track with our 125/150's..once i changed my slide,and shared it with the others on ktm 125/150 fb group,many of us are reaping the benefits of your work..i joined the site mainly to comment on this post..i think if you look into it,you'll find the needle jet is S-1,not 7..i got a big old magnifying glass i use to read them,. i will be pulling my jet in the next couple days to see if my 18 tc125,with a ktm 150 kit,came stock with S-1 or S-4..to get to the point,i think you saw a 7,where it is actually a 1..the only two options are s-4 and s-1..if i'm right,you can update your notes..if i'm wrong,please let me know...thanks again bud..

Blue, I remember that bike pretty well. It' was a new TC 125 that her parents bought her to race the GNCC series on. The OEM needle jet that came in that bike, was an S-7. It surprised me, because all of the other KTM model bikes came with an S-1, up until that bike. I just chalked it up to being a Husky brand thing, and put a jetting combo in it that I thought would work in that carb. Ultimately though, we wound up using a 38mm Keihin PWK on that bike, and she won the GNCC women's AM championship with it. 

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MONEY.
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MONEY. 1/10/2025 7:32am
1/10/2025 7:32am

We ran ours 60:1 and it fixed all those issues on our 2020 SX150. No detonation issues but we change top ends every 15-20hrs. Good luck! 

crusher773
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crusher773 1/10/2025 8:22am
1/10/2025 8:22am

We have a 2020 that we 150'd this summer and did this carb setup.  Ran strong all year never any issues runs great.

Chain ChaTTer
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Chain ChaTTer 1/10/2025 5:19pm
1/10/2025 5:19pm
crusher773 wrote:

We have a 2020 that we 150'd this summer and did this carb setup.  Ran strong all year never any issues runs great.

Which set up boss? Diggers? Going through it with this carb currently...having read this thread I'm hoping it's the jet block 

Lots of borr,borrrr borrrrr...

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