Picking Up a 2019 KTM 150sx...What to Know

bics56
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Coraopolis, PA US
12/21/2020 4:22pm Edited Date/Time 12/25/2020 6:05pm
Tomorrow I should be picking up a 2019 KTM 150sx. I found a nice clean stock bike with 33 hours. I been riding a TC250 two stroke for the last couple years (coming off of 10 years on 450's) and .this last year I got a yz125 to dabble in the small bore bikes for my second bike. I loved riding the yz and got intrigued by the 150sx and here I am now. I mostly ride for fun at local practice tracks. I may race a couple times a year in the +40 open class. So the bike is primarily for fun. Looking for some insight on what to expect for performance, setup, and light mods.
2
|
12/21/2020 4:35pm
I recommend a flywheel weight.

The Lectron carb makes a worthwhile difference.
4
12/21/2020 4:52pm
Most likely if the jetting is stock it will have a rich burble off the pilot jet to the needle transition. Go down one on the pilot and to the 2nd clip pos for the needle.
alien
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US
12/21/2020 5:43pm
I have a 2020 150 sx and I will tell you, don't try to jet it until you replace the jet block gasket. After that the jetting chart in the owners book will get you very close. The 150 sx loves a 500 or larger main jet below 80 deg F. I sold my 450 and this is my only bike now. I race the 40+ and 50+ and can beat anyone I could beat when I was on on the 450 it just takes a little more effort but it's more rewarding. This may be a little controversial , it goes against the mainstream wisdom on setting up the WP xact fork but I run 7.5 bar of air in the fork and a 4.6 kg spring in the rear. I weigh 190lbs. and I am a vet A rider. These settings will not feel like a yamaha but it will be rideable. Even at 190 lbs. I couldn't get the forks to follow the ground at 8.1 bar. At 33 hours you my want to replace the piston soon, ktm sells a complete piston kit for around $270.00, it comes with different base gaskets to set x height. I just use the .5 mm gasket every time and the vertex piston kit. The procircuit shorty muffler will help it rev a little quicker and punch up the low end. OK I saved the best for last, if you are a moto guy and want max performance install the red power valve spring and set adjuster at two turns in from all the way out. The 150 is a great little bike, enjoy.
8
Rickyisms
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12/21/2020 5:43pm Edited Date/Time 12/21/2020 8:14pm
Play with sprocket sizes. In stock form the 150 signs off earlier than most 125s, but packs a good punch off idle.

A longer silencer also helps the over rev. My favorite combo on the 150 has been the stock expansion chamber with a turbinecore spark arrestor. In harescrambles I really noticed I was able to rev the bike further in each gear with usable power compared to a shorty.

If you can find a Keihin off the 2016 bikes and get it jetted correctly you can save some money vs having to buy a lectron. I jetted my 150 for average temps here in Fl (Hot and humid) and the bike has ran fine in FL, WV, NC, and TN in the winter. Just had to play with the air/fuel screw for a couple minutes at each place.

Be very cautious of torque specs for the oil drains, I learned the hard way that KTMs are more prone to ripping out threads compared to Jap bikes. More places to be careful are the top engine mounts and the bolts that mount the slave cylinder to the case.

Flush the fluid in the hydro clutch often. It gets dirty pretty quick with the abuse a clutch takes in a small bore. Clean fluid will make a huge difference at the lever in terms of feel. I do mine about every 20 hours.

Play with the adjustment screw for the Powervalve! They’re only a couple bucks a piece. I recommend starting with the red screw, get the head corrected for good fuel. I had my guy clean up the engine for around 102-105 octane to keep the bike reliable, and be able to run good fuel. I usually run a mix of leaded 110 and rec 90.

Have fun with the bike! The 150s are a blast, be sure to throw up a pic or two of the bike!
3

The Shop

12/21/2020 5:57pm
All you need to know is you’re about to have the time of your life! And there’s some helpful carb advice from the gentlemen above.
1
12/21/2020 6:30pm Edited Date/Time 12/21/2020 6:33pm
Rickyisms wrote:
Play with sprocket sizes. In stock form the 150 signs off earlier than most 125s, but packs a good punch off idle. A longer silencer also...
Play with sprocket sizes. In stock form the 150 signs off earlier than most 125s, but packs a good punch off idle.

A longer silencer also helps the over rev. My favorite combo on the 150 has been the stock expansion chamber with a turbinecore spark arrestor. In harescrambles I really noticed I was able to rev the bike further in each gear with usable power compared to a shorty.

If you can find a Keihin off the 2016 bikes and get it jetted correctly you can save some money vs having to buy a lectron. I jetted my 150 for average temps here in Fl (Hot and humid) and the bike has ran fine in FL, WV, NC, and TN in the winter. Just had to play with the air/fuel screw for a couple minutes at each place.

Be very cautious of torque specs for the oil drains, I learned the hard way that KTMs are more prone to ripping out threads compared to Jap bikes. More places to be careful are the top engine mounts and the bolts that mount the slave cylinder to the case.

Flush the fluid in the hydro clutch often. It gets dirty pretty quick with the abuse a clutch takes in a small bore. Clean fluid will make a huge difference at the lever in terms of feel. I do mine about every 20 hours.

Play with the adjustment screw for the Powervalve! They’re only a couple bucks a piece. I recommend starting with the red screw, get the head corrected for good fuel. I had my guy clean up the engine for around 102-105 octane to keep the bike reliable, and be able to run good fuel. I usually run a mix of leaded 110 and rec 90.

Have fun with the bike! The 150s are a blast, be sure to throw up a pic or two of the bike!
Interesting that you mentioned the gearing and it revving out real fast. I ordered a 14t front for my '21. It has a 13t stock and it does what my 06 yz125 did when it was ported and modded into a 144.

With the stock 13t on my yz144 I noticed that in the lower gears 1st thru 3rd. It would spin up too fast and rev out quickly and wheel spin breaking traction easily. You would run out of gearing in the lower gears before you ran out of power.

So you ended up short shifting through the first three gears to quickly. You ended up being a gear to high because of this. The ktm 150 sx does this same thing with the 13t front sprocket. I'm going to put on a 14t front like i did my yz144.

When I did that to my yz144 it corrected the gearing ratio and brought it back to how it was. When my yz125 was stock. I'm pretty positive this will fix the sx 150's gearing. Going to a 14t front is like taking 3 teeth off the rear.

The older ktm 150's before 2016 came with 14t fronts.
2
MxKing809
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12/21/2020 7:38pm Edited Date/Time 12/21/2020 7:38pm
1) Notch the slide. There is a bunch of stuff on KTM Talk about it. It cleanes up that off-throttle gargle without leaning out the jetting.

2) I second the gearing advice. There is ample bottom but I was out of 2nd too fast IMO. Instead of gearing it down, I went up 2 teeth in the back. This paired with a shorty silencer made 3rd a 2nd on steroids. Pulls hard in tight corners and has that long pull you'd expect out of 3rd.

Also, there seemed to be a gap between 3rd and 4th with stock jetting. I would be pulling 3rd and feel the plateau, and with the rpms still on the pipe, feel like 4th took a bit to get back in the meat. There was this soft spot where I couldn't keep it pinging. The higher teeth in back solved that.

Other than that, I have 15 hours on mine that I picked up last summer. Running stock suspension with the 110 purple Sunoco leaded fuel mixed 50/50 with 93 - and the recommended Motorex oil at 32:1. Let's face it, these bikes get wrung out. I'll do things like Notch the slide and stuff that allow me to run it a bit rich up top.

1
JohnMatrix
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12/21/2020 8:07pm
Lectron carb and a pc pipe is a nice setup on the 150. Those mods on mine stretch out the top end nicely. Seems to give it a little bit wider window of power.
Rickyisms
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12/21/2020 8:11pm
MxKing809 wrote:
1) Notch the slide. There is a bunch of stuff on KTM Talk about it. It cleanes up that off-throttle gargle without leaning out the jetting...
1) Notch the slide. There is a bunch of stuff on KTM Talk about it. It cleanes up that off-throttle gargle without leaning out the jetting.

2) I second the gearing advice. There is ample bottom but I was out of 2nd too fast IMO. Instead of gearing it down, I went up 2 teeth in the back. This paired with a shorty silencer made 3rd a 2nd on steroids. Pulls hard in tight corners and has that long pull you'd expect out of 3rd.

Also, there seemed to be a gap between 3rd and 4th with stock jetting. I would be pulling 3rd and feel the plateau, and with the rpms still on the pipe, feel like 4th took a bit to get back in the meat. There was this soft spot where I couldn't keep it pinging. The higher teeth in back solved that.

Other than that, I have 15 hours on mine that I picked up last summer. Running stock suspension with the 110 purple Sunoco leaded fuel mixed 50/50 with 93 - and the recommended Motorex oil at 32:1. Let's face it, these bikes get wrung out. I'll do things like Notch the slide and stuff that allow me to run it a bit rich up top.

Yup I do 32:1 here with Castor in my 125 and 150 as well. With being in the FL sand I need all the lubricity I can get. Do you have any headwork done to run higher octane? Have you ran 93 straight up and noticed a difference between the race fuel mix and just 93?

I stopped using ethanol fuel all together after talking with an engine builder about how the percentage of ethanol content can lean the bike out.
Rickyisms
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12/21/2020 8:12pm
alien wrote:
I have a 2020 150 sx and I will tell you, don't try to jet it until you replace the jet block gasket. After that the...
I have a 2020 150 sx and I will tell you, don't try to jet it until you replace the jet block gasket. After that the jetting chart in the owners book will get you very close. The 150 sx loves a 500 or larger main jet below 80 deg F. I sold my 450 and this is my only bike now. I race the 40+ and 50+ and can beat anyone I could beat when I was on on the 450 it just takes a little more effort but it's more rewarding. This may be a little controversial , it goes against the mainstream wisdom on setting up the WP xact fork but I run 7.5 bar of air in the fork and a 4.6 kg spring in the rear. I weigh 190lbs. and I am a vet A rider. These settings will not feel like a yamaha but it will be rideable. Even at 190 lbs. I couldn't get the forks to follow the ground at 8.1 bar. At 33 hours you my want to replace the piston soon, ktm sells a complete piston kit for around $270.00, it comes with different base gaskets to set x height. I just use the .5 mm gasket every time and the vertex piston kit. The procircuit shorty muffler will help it rev a little quicker and punch up the low end. OK I saved the best for last, if you are a moto guy and want max performance install the red power valve spring and set adjuster at two turns in from all the way out. The 150 is a great little bike, enjoy.
For the PV adjustment do you mean crank it clockwise all the way, and then two turns back counter clockwise?
CarlinoJoeVideo
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12/21/2020 8:32pm
alien wrote:
I have a 2020 150 sx and I will tell you, don't try to jet it until you replace the jet block gasket. After that the...
I have a 2020 150 sx and I will tell you, don't try to jet it until you replace the jet block gasket. After that the jetting chart in the owners book will get you very close. The 150 sx loves a 500 or larger main jet below 80 deg F. I sold my 450 and this is my only bike now. I race the 40+ and 50+ and can beat anyone I could beat when I was on on the 450 it just takes a little more effort but it's more rewarding. This may be a little controversial , it goes against the mainstream wisdom on setting up the WP xact fork but I run 7.5 bar of air in the fork and a 4.6 kg spring in the rear. I weigh 190lbs. and I am a vet A rider. These settings will not feel like a yamaha but it will be rideable. Even at 190 lbs. I couldn't get the forks to follow the ground at 8.1 bar. At 33 hours you my want to replace the piston soon, ktm sells a complete piston kit for around $270.00, it comes with different base gaskets to set x height. I just use the .5 mm gasket every time and the vertex piston kit. The procircuit shorty muffler will help it rev a little quicker and punch up the low end. OK I saved the best for last, if you are a moto guy and want max performance install the red power valve spring and set adjuster at two turns in from all the way out. The 150 is a great little bike, enjoy.
Rickyisms wrote:
For the PV adjustment do you mean crank it clockwise all the way, and then two turns back counter clockwise?
Turn the powerValve all the way out, counterclockwise and it will stop, it won’t fall out. From that point you turn it in for your adjusted setting.

To get a better feel I’d like to do a lap or two and bring the tool to the track do a full turn in or out so you can feel the difference of where the power band hits
1
bics56
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12/21/2020 10:09pm
So is the PC pipe the go to pipe for these bikes?
Bruce372
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12/22/2020 8:23am
bics56 wrote:
So is the PC pipe the go to pipe for these bikes?
Fmf fatty with the pc shorty is very good combo. Lots of silencers actually loose power over stock.

Jet the mikuni or get a pwk. I didn't like lectron on my 150
1
1
dcg141
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12/22/2020 8:36am
If you keep the Mikuni you need to get this. It really helps fix a lot of the issues with that carb. The Mikuni fixed is very good. JD Jetting jet block kit I have used his jetting kit as well with good results.
5
AJ565
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12/22/2020 11:27am
We got the jetting sorted out. Here is where the info is, don't waste your money on buying different carbs.

https://www.vitalmx.com/forums/Tech-Help-Race-Shop,42/KTM-HUS-125-150-2…

Gearing wise if you want to go up one tooth in the rear or down in the rear get a whole new front, rear and chain. Bump up to a 14t front sprocket and get the rear accordingly to what you want to do in the rear. I've ridden them with stock, +1 and +2 and I felt stock was the best of the 3 and really wanted to go -1 in the rear.

The reason I say bump up the front is it changes chain angles and frees up the rear suspension under load and in back to back testing is noticeable. If you need help with the math on it let me know. Its kinda easy though. example: if it has 13t front and a 50t rear then its 50/13= 3.85. If you want to keep close to the same ratio it would be a 14t and 54t which would put you at a 3.86 ratio.

Chassis wise it also likes the Ride Engineering steering damper. It will help it from trying to climb out of ruts.

Get the suspension set up for you. The shock spring will be undersprung for anyone thats not 120lbs. The Ride Engineering link will transform the way the bike handles and cut down on the rear swap going hard through braking bumps.
1
12/22/2020 8:02pm Edited Date/Time 12/22/2020 8:05pm
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271 to a 4274. One size leaner on the slide from a 4 to a 5. Up two mains from 470 to 490 and one richer on the pilot from a 30 to 32.5

My 21 all ready comes with the S4 needle jet.
I run my bike on trick 100 it's a 100 unleaded non ethanol fuel at 40:1 on 927.
I like to ride my 150 like a 125 and I have a 14t front coming. All ready did the jd jet block gasket swap.
Just don't want to squeak my new bike with only 5 hrs on it.

It runs okay right now but i may have gone the wrong direction. When I first got it, it had this bad rich burbling at 1/4 throttle. So i went down one on the pilot to a 27.5 and it helped a little bit. So i went to clip position #2 and it felt better. But this was in early August and it was 80 degrees.

The last couple times I rode it especially like a month ago and it was 34 degrees in the morning. It had the hesitation bog to the point of almost stalling out around 1/4 throttle. It got a little better when the temp warmed up. Oh yea and it seemed like more than usual it was hard to start. I know when it's really cold they are sometimes a pain. For that first start of the day but it was refusing at first.


AJ565
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12/22/2020 9:11pm
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271...
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271 to a 4274. One size leaner on the slide from a 4 to a 5. Up two mains from 470 to 490 and one richer on the pilot from a 30 to 32.5

My 21 all ready comes with the S4 needle jet.
I run my bike on trick 100 it's a 100 unleaded non ethanol fuel at 40:1 on 927.
I like to ride my 150 like a 125 and I have a 14t front coming. All ready did the jd jet block gasket swap.
Just don't want to squeak my new bike with only 5 hrs on it.

It runs okay right now but i may have gone the wrong direction. When I first got it, it had this bad rich burbling at 1/4 throttle. So i went down one on the pilot to a 27.5 and it helped a little bit. So i went to clip position #2 and it felt better. But this was in early August and it was 80 degrees.

The last couple times I rode it especially like a month ago and it was 34 degrees in the morning. It had the hesitation bog to the point of almost stalling out around 1/4 throttle. It got a little better when the temp warmed up. Oh yea and it seemed like more than usual it was hard to start. I know when it's really cold they are sometimes a pain. For that first start of the day but it was refusing at first.


Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
T-Fish
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12/22/2020 9:42pm
Even better than sliced bread.


4
12/23/2020 8:55am
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271...
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271 to a 4274. One size leaner on the slide from a 4 to a 5. Up two mains from 470 to 490 and one richer on the pilot from a 30 to 32.5

My 21 all ready comes with the S4 needle jet.
I run my bike on trick 100 it's a 100 unleaded non ethanol fuel at 40:1 on 927.
I like to ride my 150 like a 125 and I have a 14t front coming. All ready did the jd jet block gasket swap.
Just don't want to squeak my new bike with only 5 hrs on it.

It runs okay right now but i may have gone the wrong direction. When I first got it, it had this bad rich burbling at 1/4 throttle. So i went down one on the pilot to a 27.5 and it helped a little bit. So i went to clip position #2 and it felt better. But this was in early August and it was 80 degrees.

The last couple times I rode it especially like a month ago and it was 34 degrees in the morning. It had the hesitation bog to the point of almost stalling out around 1/4 throttle. It got a little better when the temp warmed up. Oh yea and it seemed like more than usual it was hard to start. I know when it's really cold they are sometimes a pain. For that first start of the day but it was refusing at first.


AJ565 wrote:
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and...
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into the low 30's and get up to the 90's. Most of the time it's gonna be in the 40's thru 70's.

I was thinking about just going the pwk route instead. Partzilla wants $134 for that 5.0 Suzuki slide. Jd jetting had'em listed for $75 but it's listed as back ordered.

I know the tmx - x style carb can be made good. But it was like night n day with my friends 06 cr 125 n 250 putting the pwk air striker on them.

It seemed like in 16 it ran better with the pwk. So why not just get one an put the 16 settings in it. Or is that the same thing jd jetting sales when you buy the pwk from him?

I rode my friends '18 250 sx with a lectron on it. It's the newest version and it ran good. But it really didn't seem that much or any better than my stock mikuni on my '21 250sx. So i wasn't that impressed by it.

The stic sounds cool but it's kinda expensive for just being a different jet metering block setup. That and it seems like it's still kinda in the testing stages.

Rickyisms
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12/23/2020 9:13am
T-Fish wrote:
Even better than sliced bread. [img]https://p.vitalmx.com/photos/forums/2020/12/22/467423/s1200_DA7799AE_ADB1_4A07_A5AF_97B7F722DD04.jpg[/img]
Even better than sliced bread.


What A/F mixture screw is that?
AJ565
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San Antonio, TX US
12/23/2020 9:36am
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271...
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271 to a 4274. One size leaner on the slide from a 4 to a 5. Up two mains from 470 to 490 and one richer on the pilot from a 30 to 32.5

My 21 all ready comes with the S4 needle jet.
I run my bike on trick 100 it's a 100 unleaded non ethanol fuel at 40:1 on 927.
I like to ride my 150 like a 125 and I have a 14t front coming. All ready did the jd jet block gasket swap.
Just don't want to squeak my new bike with only 5 hrs on it.

It runs okay right now but i may have gone the wrong direction. When I first got it, it had this bad rich burbling at 1/4 throttle. So i went down one on the pilot to a 27.5 and it helped a little bit. So i went to clip position #2 and it felt better. But this was in early August and it was 80 degrees.

The last couple times I rode it especially like a month ago and it was 34 degrees in the morning. It had the hesitation bog to the point of almost stalling out around 1/4 throttle. It got a little better when the temp warmed up. Oh yea and it seemed like more than usual it was hard to start. I know when it's really cold they are sometimes a pain. For that first start of the day but it was refusing at first.


AJ565 wrote:
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and...
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into...
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into the low 30's and get up to the 90's. Most of the time it's gonna be in the 40's thru 70's.

I was thinking about just going the pwk route instead. Partzilla wants $134 for that 5.0 Suzuki slide. Jd jetting had'em listed for $75 but it's listed as back ordered.

I know the tmx - x style carb can be made good. But it was like night n day with my friends 06 cr 125 n 250 putting the pwk air striker on them.

It seemed like in 16 it ran better with the pwk. So why not just get one an put the 16 settings in it. Or is that the same thing jd jetting sales when you buy the pwk from him?

I rode my friends '18 250 sx with a lectron on it. It's the newest version and it ran good. But it really didn't seem that much or any better than my stock mikuni on my '21 250sx. So i wasn't that impressed by it.

The stic sounds cool but it's kinda expensive for just being a different jet metering block setup. That and it seems like it's still kinda in the testing stages.

That’s a solid jetting start then for that range. The Lectron takes away a lot of the hit when you ride it back to back against a tunes makuni.

RB designs can cut your stock slide to 5.0 for $25 if you google them.
2
FGR01
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12/23/2020 10:14am
Rickyisms wrote:
What A/F mixture screw is that?
That's the optional extended EZ-adjust one that JD and/or George sell and include with the STIC complete carbs.
1
Bruce372
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12/23/2020 10:18am
AJ565 wrote:
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and...
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into...
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into the low 30's and get up to the 90's. Most of the time it's gonna be in the 40's thru 70's.

I was thinking about just going the pwk route instead. Partzilla wants $134 for that 5.0 Suzuki slide. Jd jetting had'em listed for $75 but it's listed as back ordered.

I know the tmx - x style carb can be made good. But it was like night n day with my friends 06 cr 125 n 250 putting the pwk air striker on them.

It seemed like in 16 it ran better with the pwk. So why not just get one an put the 16 settings in it. Or is that the same thing jd jetting sales when you buy the pwk from him?

I rode my friends '18 250 sx with a lectron on it. It's the newest version and it ran good. But it really didn't seem that much or any better than my stock mikuni on my '21 250sx. So i wasn't that impressed by it.

The stic sounds cool but it's kinda expensive for just being a different jet metering block setup. That and it seems like it's still kinda in the testing stages.

AJ565 wrote:
That’s a solid jetting start then for that range. The Lectron takes away a lot of the hit when you ride it back to back against...
That’s a solid jetting start then for that range. The Lectron takes away a lot of the hit when you ride it back to back against a tunes makuni.

RB designs can cut your stock slide to 5.0 for $25 if you google them.
Yeah, the lectron runs clean but does take away some of the two stroke feel. Plus, to run it you need new cable, airbox boot, standard size Allen's and the choke is on the wrong size
FGR01
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12/23/2020 10:22am
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271...
So i read the jetting thread so you're saying on my '21 150 sx. I should go 3 sizes leaner on the needle from a 4271 to a 4274. One size leaner on the slide from a 4 to a 5. Up two mains from 470 to 490 and one richer on the pilot from a 30 to 32.5

My 21 all ready comes with the S4 needle jet.
I run my bike on trick 100 it's a 100 unleaded non ethanol fuel at 40:1 on 927.
I like to ride my 150 like a 125 and I have a 14t front coming. All ready did the jd jet block gasket swap.
Just don't want to squeak my new bike with only 5 hrs on it.

It runs okay right now but i may have gone the wrong direction. When I first got it, it had this bad rich burbling at 1/4 throttle. So i went down one on the pilot to a 27.5 and it helped a little bit. So i went to clip position #2 and it felt better. But this was in early August and it was 80 degrees.

The last couple times I rode it especially like a month ago and it was 34 degrees in the morning. It had the hesitation bog to the point of almost stalling out around 1/4 throttle. It got a little better when the temp warmed up. Oh yea and it seemed like more than usual it was hard to start. I know when it's really cold they are sometimes a pain. For that first start of the day but it was refusing at first.


AJ565 wrote:
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and...
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into...
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into the low 30's and get up to the 90's. Most of the time it's gonna be in the 40's thru 70's.

I was thinking about just going the pwk route instead. Partzilla wants $134 for that 5.0 Suzuki slide. Jd jetting had'em listed for $75 but it's listed as back ordered.

I know the tmx - x style carb can be made good. But it was like night n day with my friends 06 cr 125 n 250 putting the pwk air striker on them.

It seemed like in 16 it ran better with the pwk. So why not just get one an put the 16 settings in it. Or is that the same thing jd jetting sales when you buy the pwk from him?

I rode my friends '18 250 sx with a lectron on it. It's the newest version and it ran good. But it really didn't seem that much or any better than my stock mikuni on my '21 250sx. So i wasn't that impressed by it.

The stic sounds cool but it's kinda expensive for just being a different jet metering block setup. That and it seems like it's still kinda in the testing stages.

The general condition of the stock 125/150 jetting is that you have a rich slide and rich needle and that puts you in the boat of making the pilot and main lean to work around that. The problem, as you've discovered, is then your pilot is excessively lean and you get hard starting when it's cold out and possibly your main is lean and the bike gets flat on top.

With the jetting in the thread AJ posted, you're leaning out the slide and needle and can then run a pilot and main which are more in the correct range of what the bike needs because you're not trying to work around an excessively rich slide/needle combo.
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2stmark
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Waterford, MI US
12/24/2020 5:02am
T-Fish wrote:
Even better than sliced bread. [img]https://p.vitalmx.com/photos/forums/2020/12/22/467423/s1200_DA7799AE_ADB1_4A07_A5AF_97B7F722DD04.jpg[/img]
Even better than sliced bread.


I have this on my 16' 150 sx & it continues to amaze me everytime i ride
MxKing809
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12/24/2020 6:21am
AJ565 wrote:
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and...
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into...
Where i live usually most of my riding is usually around sea level up to 2500 occasionally higher due to mountain riding. It can be into the low 30's and get up to the 90's. Most of the time it's gonna be in the 40's thru 70's.

I was thinking about just going the pwk route instead. Partzilla wants $134 for that 5.0 Suzuki slide. Jd jetting had'em listed for $75 but it's listed as back ordered.

I know the tmx - x style carb can be made good. But it was like night n day with my friends 06 cr 125 n 250 putting the pwk air striker on them.

It seemed like in 16 it ran better with the pwk. So why not just get one an put the 16 settings in it. Or is that the same thing jd jetting sales when you buy the pwk from him?

I rode my friends '18 250 sx with a lectron on it. It's the newest version and it ran good. But it really didn't seem that much or any better than my stock mikuni on my '21 250sx. So i wasn't that impressed by it.

The stic sounds cool but it's kinda expensive for just being a different jet metering block setup. That and it seems like it's still kinda in the testing stages.

FGR01 wrote:
The general condition of the stock 125/150 jetting is that you have a rich slide and rich needle and that puts you in the boat of...
The general condition of the stock 125/150 jetting is that you have a rich slide and rich needle and that puts you in the boat of making the pilot and main lean to work around that. The problem, as you've discovered, is then your pilot is excessively lean and you get hard starting when it's cold out and possibly your main is lean and the bike gets flat on top.

With the jetting in the thread AJ posted, you're leaning out the slide and needle and can then run a pilot and main which are more in the correct range of what the bike needs because you're not trying to work around an excessively rich slide/needle combo.
Notch your slide.

Fixes this in-between decision to lean out jets. Trust me.
1
Tomok
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Epping, NH US
12/24/2020 6:58am
I'm using AJ's jetting on a 2019 250SX. Bike runs amazing! I never have to mess with it besides a slight air screw tweak or a main jet change due to temps or sand track requirements. 2 thumbs up!
piscokid
Posts
301
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Location
OH US
12/24/2020 7:05am Edited Date/Time 12/24/2020 7:06am
Lots of good advice on jetting here. These bikes are amazing when you get the jetting spot on. Not a fan of Lectron's. They have their place when riding where there is significant altitude change (like riding in the mountains and moving up elevations) but in my opinion, (flame away!) that if one thinks the bike runs better with a lectron, the bike wasn't jetted correctly in the first place.
2
mxstate
Posts
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Location
FL US
12/24/2020 8:43am Edited Date/Time 12/24/2020 8:45am
AJ565 wrote:
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and...
Yes. It all works well together and there are a lot of bikes running the jetting I have in that thread. You’ll have to try and see if you can get away with it in your area and temps, but try a 500 main. These bikes like big mains and in a 125 that’s where you are a lot. The leaner needle and slide clean up the bottom end and the richer pilot keeps things where they should be. I wish more people that have swapped to that jetting would report back, but normally they run the jetting and don’t comment anymore since their issue was resolved.
Not trying to steer anybody to spend $$$ on a Keihin or Lectron but AJ's thread is spot on

Works wonders on my 19 TC 250.
Re-jetted a friend's 150 SX (2017) -per the AJ]s specs
Fast A rider and he was beyond thrilled by how clean and crisp it is running now
Was so rich and gargling/inconsistent prior the mods.
We're both in FL so elevation changes not in the equation but large swings in temp and humidity and besides maybe A/S tweak if you're super finicky, these jetting specs are the best bang for the buck.

The TMX has been on YZ 125 forever and nobody ever complained about it.
KTM/Husqy just came up with some questionable stock settings


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FGR01
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12/24/2020 8:54am
MxKing809 wrote:
Notch your slide.

Fixes this in-between decision to lean out jets. Trust me.
I'm running the Digger/AJ jetting from the other thread in my 2021 TC125, with some slight richening tweaks here and there to account for AvGas. The only part I haven't done is the slide notch and corresponding leaning of the pilot, basically because the bike runs so well I don't feel compelled to do it. Also, I ride MX only pretty wide open the whole time so I'm probably not overly sensitive about the absolute best performance on the pilot jet.

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