125/150/250/300 KTM/HUS/GG jetting thread

AJ565
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AJ565 5/9/2022 7:02am
5/9/2022 7:02am
Tuplavee wrote:
Recommended sea level jetting for temperatures 10-25 Celsius (50-75F) ? Novice level mx and sometimes single track. TC250 2017 Stock slide, stock needle jet. Currently 440...
Recommended sea level jetting for temperatures 10-25 Celsius (50-75F) ?
Novice level mx and sometimes single track.

TC250 2017
Stock slide, stock needle jet.
Currently 440 MJ, 42,5 PJ, 6BFY43-73 - 2nd from top.

I did look for 5.0-5.75 slides and S4 needle jet+needle and jets.. but seems costly if not 100% sure how it work
The 5.75 slide setup on the first page. I’m at 600’ and it runs great.
Tuplavee
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Tuplavee 5/10/2022 1:41am
5/10/2022 1:41am
Tuplavee wrote:
Recommended sea level jetting for temperatures 10-25 Celsius (50-75F) ? Novice level mx and sometimes single track. TC250 2017 Stock slide, stock needle jet. Currently 440...
Recommended sea level jetting for temperatures 10-25 Celsius (50-75F) ?
Novice level mx and sometimes single track.

TC250 2017
Stock slide, stock needle jet.
Currently 440 MJ, 42,5 PJ, 6BFY43-73 - 2nd from top.

I did look for 5.0-5.75 slides and S4 needle jet+needle and jets.. but seems costly if not 100% sure how it work
AJ565 wrote:
The 5.75 slide setup on the first page. I’m at 600’ and it runs great.
Kind of would want to try something with stock slide first for this summer.
Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound cleanest.
My first 2-stroke so not really anything to compare, it doesnt need to be perfect or most powerful... just cleanish, responsive and "safe".

How low it is safe to go with pilot jet? 37,5 ok with stock slide and needle jet?

Getting all the bits and pieces with new slide would be +200EUR... I'm not sure if I can justify the benefit
AJ565
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AJ565 5/10/2022 5:50am
5/10/2022 5:50am
Tuplavee wrote:
Recommended sea level jetting for temperatures 10-25 Celsius (50-75F) ? Novice level mx and sometimes single track. TC250 2017 Stock slide, stock needle jet. Currently 440...
Recommended sea level jetting for temperatures 10-25 Celsius (50-75F) ?
Novice level mx and sometimes single track.

TC250 2017
Stock slide, stock needle jet.
Currently 440 MJ, 42,5 PJ, 6BFY43-73 - 2nd from top.

I did look for 5.0-5.75 slides and S4 needle jet+needle and jets.. but seems costly if not 100% sure how it work
AJ565 wrote:
The 5.75 slide setup on the first page. I’m at 600’ and it runs great.
Tuplavee wrote:
Kind of would want to try something with stock slide first for this summer. Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound...
Kind of would want to try something with stock slide first for this summer.
Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound cleanest.
My first 2-stroke so not really anything to compare, it doesnt need to be perfect or most powerful... just cleanish, responsive and "safe".

How low it is safe to go with pilot jet? 37,5 ok with stock slide and needle jet?

Getting all the bits and pieces with new slide would be +200EUR... I'm not sure if I can justify the benefit
You’ll never get it right, the slide is the problem. Countless people have tried and they are just trying to put a bandaid on the problem inside of fixing it. You can go back through the thread and see that and then they swap the parts and agree that it’s worth it. If cost is a factor for you then way back in this thread somewhere there is measurements to modify the slide yourself or you can even send it out and have it modified pretty cheap.
Tuplavee
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Tuplavee 5/10/2022 7:39am
5/10/2022 7:39am
AJ565 wrote:
The 5.75 slide setup on the first page. I’m at 600’ and it runs great.
Tuplavee wrote:
Kind of would want to try something with stock slide first for this summer. Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound...
Kind of would want to try something with stock slide first for this summer.
Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound cleanest.
My first 2-stroke so not really anything to compare, it doesnt need to be perfect or most powerful... just cleanish, responsive and "safe".

How low it is safe to go with pilot jet? 37,5 ok with stock slide and needle jet?

Getting all the bits and pieces with new slide would be +200EUR... I'm not sure if I can justify the benefit
AJ565 wrote:
You’ll never get it right, the slide is the problem. Countless people have tried and they are just trying to put a bandaid on the problem...
You’ll never get it right, the slide is the problem. Countless people have tried and they are just trying to put a bandaid on the problem inside of fixing it. You can go back through the thread and see that and then they swap the parts and agree that it’s worth it. If cost is a factor for you then way back in this thread somewhere there is measurements to modify the slide yourself or you can even send it out and have it modified pretty cheap.
No need to perfect, just optimal with stock partsSmile

Ok, I'll at least keep looking for slides, maybe my wallet will look another way sometime...
So 5.75 would be only route for all temperatures even at 0C/32F? Not 5.0 or 5.5?

The Shop

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AJ565
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AJ565 5/10/2022 9:11am
5/10/2022 9:11am
Tuplavee wrote:
Kind of would want to try something with stock slide first for this summer. Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound...
Kind of would want to try something with stock slide first for this summer.
Full throttle it seems fine enough, but 1/4 and 1/2 doesnt sound cleanest.
My first 2-stroke so not really anything to compare, it doesnt need to be perfect or most powerful... just cleanish, responsive and "safe".

How low it is safe to go with pilot jet? 37,5 ok with stock slide and needle jet?

Getting all the bits and pieces with new slide would be +200EUR... I'm not sure if I can justify the benefit
AJ565 wrote:
You’ll never get it right, the slide is the problem. Countless people have tried and they are just trying to put a bandaid on the problem...
You’ll never get it right, the slide is the problem. Countless people have tried and they are just trying to put a bandaid on the problem inside of fixing it. You can go back through the thread and see that and then they swap the parts and agree that it’s worth it. If cost is a factor for you then way back in this thread somewhere there is measurements to modify the slide yourself or you can even send it out and have it modified pretty cheap.
Tuplavee wrote:
No need to perfect, just optimal with stock parts:) Ok, I'll at least keep looking for slides, maybe my wallet will look another way sometime... So...
No need to perfect, just optimal with stock partsSmile

Ok, I'll at least keep looking for slides, maybe my wallet will look another way sometime...
So 5.75 would be only route for all temperatures even at 0C/32F? Not 5.0 or 5.5?
You can go with the 5.5 slide setup if you’d like as well. I’ve run the 5.75 slide in the upper 30’s and needed to move the clip on the needle one position and put one side bigger pilot in it.
2
bdavis354
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bdavis354 5/10/2022 1:23pm
5/10/2022 1:23pm
Im going to try the red spring with AJ’s jetting. Have a few hrs on full jetting recommendation with slide, NJ, JN, PJ, spring was yellow at 1.5in going to try red spring at 1.75 in and may swap from 32.5PJ to 35PJ but not yet. Running t4 @60:1 w/Motorex. Once im through with this fuel I have to burn im going to dial jetting to T2 for convenience. My son is moving onto a yz65 so would be nice to not have a chemistry lab of fuel to keep track of. Any pointers or things to note with red spring and T2 jetting thoughts?
bdavis354
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bdavis354 5/10/2022 1:24pm
5/10/2022 1:24pm


AJ565
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AJ565 5/10/2022 2:05pm
5/10/2022 2:05pm
bdavis354 wrote:
Im going to try the red spring with AJ’s jetting. Have a few hrs on full jetting recommendation with slide, NJ, JN, PJ, spring was yellow...
Im going to try the red spring with AJ’s jetting. Have a few hrs on full jetting recommendation with slide, NJ, JN, PJ, spring was yellow at 1.5in going to try red spring at 1.75 in and may swap from 32.5PJ to 35PJ but not yet. Running t4 @60:1 w/Motorex. Once im through with this fuel I have to burn im going to dial jetting to T2 for convenience. My son is moving onto a yz65 so would be nice to not have a chemistry lab of fuel to keep track of. Any pointers or things to note with red spring and T2 jetting thoughts?
I run the same jetting with T2.
1
bdavis354
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bdavis354 5/10/2022 2:47pm
5/10/2022 2:47pm
Perfect 🤘🤘🤘
dwight955
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dwight955 5/17/2022 9:21am
5/17/2022 9:21am
Hello everyone. Proud owner of a 2022 Gas Gas MC 125, maybe 7 hours total since i got it.
I replaced all the parts as suggested on the 125/150 jetting table listed on the first page
Sitting on the stand, the bike starts first kick idles nicely, but has pretty good size bog at about half throttle. Once past the stumble the bike sounds good. This is on the stand.
I won't be able to ride bike for a couple of days. Does anyone have any advice on what it could be? First new bike and two stroke in a long time. For what it's worth, I have done nothing with P/V adjustment and the bike has the replacement CDI . Any help and or recommendations are appreciated. Thank you.
AJ565
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AJ565 5/17/2022 11:58am
5/17/2022 11:58am
dwight955 wrote:
Hello everyone. Proud owner of a 2022 Gas Gas MC 125, maybe 7 hours total since i got it. I replaced all the parts as suggested...
Hello everyone. Proud owner of a 2022 Gas Gas MC 125, maybe 7 hours total since i got it.
I replaced all the parts as suggested on the 125/150 jetting table listed on the first page
Sitting on the stand, the bike starts first kick idles nicely, but has pretty good size bog at about half throttle. Once past the stumble the bike sounds good. This is on the stand.
I won't be able to ride bike for a couple of days. Does anyone have any advice on what it could be? First new bike and two stroke in a long time. For what it's worth, I have done nothing with P/V adjustment and the bike has the replacement CDI . Any help and or recommendations are appreciated. Thank you.
It’s not a jetting problem so far. It’s been documented in this thread towards the top of this page and the last few pages, but no fix for it as of yet.
alien
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alien 5/17/2022 2:20pm
5/17/2022 2:20pm
A friend has a 22 yz125 X ,it still comes with the mikuni TMX 38 carb. From the first ride this bike ran rich and leaked fuel out the overflow tube. We tried smaller pilot jets and clip positions with little improvement. The jet block gasket was replaced ( bad right from the factory) along with the O-ring. Still no improvement so we reset the float height to 8.7 mm ,it was 6.5 stock and that did the trick . We returned to stock jetting and now the bike barks like a factory works bike and no overflow of fuel. I don't know if mikuni is using another MFG. plant but there does seem to be a quality problem with the TMX 38 in 2022 . I had a 2019 yz 125 and it was jetted perfect stock ,almost like fuel injection.
etters312
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etters312 5/27/2022 4:12pm
5/27/2022 4:12pm
AJ565 wrote:
I get a lot of emails from here and at the track about jetting for the 2 strokes. Thanks to digger for pointing me in the...

I get a lot of emails from here and at the track about jetting for the 2 strokes. Thanks to digger for pointing me in the right direction this is the currant specs. I have for everything. Its easier to start a thread With all the jetting in it to keep track of everything. Your jetting might need tweaked based on your temps and elevation, but this is a good start for you.

**Updated 4/19/23**
'17+ 125/150 jetting (‘22 bikes have a known bog, there is no jetting or carb swap combo yet that takes care of that problem. If or when it gets figured out I’ll update)


MJ 510
PJ 32.5
AS 1.75
slide 5.0 from JD Jetting
Needle 42-74 on the 2nd clip (Yamaha 284-14116-H4-00)
Needle jet S4 (KTM part #55431021400)
PV 2.25 turns in from all the way out.
Fuel mix 40:1

(credit to FGR01 for continuing to refine the small bore jetting)


On the '17+ 250's **Updated 10/13/2020**
Pump gas/race gas or straight C12

This is my current jetting. Its more refined all around and crisp down low with better top end over rev.

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
Fuel 55:1

OR

Solid jetting if you're someone that doesn't live on top end. Crisp down low out of turns pull.
MJ 490
PJ 32.5
AS 1.5 turns out
Needle jet S4 (KTM part #55431021400) stock is S1
Needle 42-75 on the 2nd clip (Yamaha part #284-14116-H5-00)
Slide 5.5 (Kawasaki part 16025-0002)
PV 1.75 turns in from all the way out
Fuel mix 50:1

300sx jetting

Pilot jet 25 and main jet 460 to start.
Slide 5.5 (Kawasaki part 16025-0002)
Needle 42-75 on the 2nd clip (Yamaha part #284-14116-H5-00)
5/32” chainsaw file to notch the front of the slide.
A/S 1.5 to start, you’ll need to adjust as needed.
 

So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all with the choke off. And with choke on it will half ass run but bogs down and shuts off. I run ethanol free 90 octane gas mixed 50:1 with castor 927. And my elevation I ride in varies from 900'-1400'. Any input would be awesome. I'm lost haha
AJ565
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AJ565 5/27/2022 5:37pm
5/27/2022 5:37pm
AJ565 wrote:
I get a lot of emails from here and at the track about jetting for the 2 strokes. Thanks to digger for pointing me in the...

I get a lot of emails from here and at the track about jetting for the 2 strokes. Thanks to digger for pointing me in the right direction this is the currant specs. I have for everything. Its easier to start a thread With all the jetting in it to keep track of everything. Your jetting might need tweaked based on your temps and elevation, but this is a good start for you.

**Updated 4/19/23**
'17+ 125/150 jetting (‘22 bikes have a known bog, there is no jetting or carb swap combo yet that takes care of that problem. If or when it gets figured out I’ll update)


MJ 510
PJ 32.5
AS 1.75
slide 5.0 from JD Jetting
Needle 42-74 on the 2nd clip (Yamaha 284-14116-H4-00)
Needle jet S4 (KTM part #55431021400)
PV 2.25 turns in from all the way out.
Fuel mix 40:1

(credit to FGR01 for continuing to refine the small bore jetting)


On the '17+ 250's **Updated 10/13/2020**
Pump gas/race gas or straight C12

This is my current jetting. Its more refined all around and crisp down low with better top end over rev.

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
Fuel 55:1

OR

Solid jetting if you're someone that doesn't live on top end. Crisp down low out of turns pull.
MJ 490
PJ 32.5
AS 1.5 turns out
Needle jet S4 (KTM part #55431021400) stock is S1
Needle 42-75 on the 2nd clip (Yamaha part #284-14116-H5-00)
Slide 5.5 (Kawasaki part 16025-0002)
PV 1.75 turns in from all the way out
Fuel mix 50:1

300sx jetting

Pilot jet 25 and main jet 460 to start.
Slide 5.5 (Kawasaki part 16025-0002)
Needle 42-75 on the 2nd clip (Yamaha part #284-14116-H5-00)
5/32” chainsaw file to notch the front of the slide.
A/S 1.5 to start, you’ll need to adjust as needed.
 

etters312 wrote:
So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all...
So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all with the choke off. And with choke on it will half ass run but bogs down and shuts off. I run ethanol free 90 octane gas mixed 50:1 with castor 927. And my elevation I ride in varies from 900'-1400'. Any input would be awesome. I'm lost haha
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right?

If you’ve done those things personally I would change to a different oil and run it 55:1 or 60:1 and see what happens. I’ve read about some having issues with 927.
etters312
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etters312 5/27/2022 5:56pm
5/27/2022 5:56pm
AJ565 wrote:
I get a lot of emails from here and at the track about jetting for the 2 strokes. Thanks to digger for pointing me in the...

I get a lot of emails from here and at the track about jetting for the 2 strokes. Thanks to digger for pointing me in the right direction this is the currant specs. I have for everything. Its easier to start a thread With all the jetting in it to keep track of everything. Your jetting might need tweaked based on your temps and elevation, but this is a good start for you.

**Updated 4/19/23**
'17+ 125/150 jetting (‘22 bikes have a known bog, there is no jetting or carb swap combo yet that takes care of that problem. If or when it gets figured out I’ll update)


MJ 510
PJ 32.5
AS 1.75
slide 5.0 from JD Jetting
Needle 42-74 on the 2nd clip (Yamaha 284-14116-H4-00)
Needle jet S4 (KTM part #55431021400)
PV 2.25 turns in from all the way out.
Fuel mix 40:1

(credit to FGR01 for continuing to refine the small bore jetting)


On the '17+ 250's **Updated 10/13/2020**
Pump gas/race gas or straight C12

This is my current jetting. Its more refined all around and crisp down low with better top end over rev.

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
Fuel 55:1

OR

Solid jetting if you're someone that doesn't live on top end. Crisp down low out of turns pull.
MJ 490
PJ 32.5
AS 1.5 turns out
Needle jet S4 (KTM part #55431021400) stock is S1
Needle 42-75 on the 2nd clip (Yamaha part #284-14116-H5-00)
Slide 5.5 (Kawasaki part 16025-0002)
PV 1.75 turns in from all the way out
Fuel mix 50:1

300sx jetting

Pilot jet 25 and main jet 460 to start.
Slide 5.5 (Kawasaki part 16025-0002)
Needle 42-75 on the 2nd clip (Yamaha part #284-14116-H5-00)
5/32” chainsaw file to notch the front of the slide.
A/S 1.5 to start, you’ll need to adjust as needed.
 

etters312 wrote:
So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all...
So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all with the choke off. And with choke on it will half ass run but bogs down and shuts off. I run ethanol free 90 octane gas mixed 50:1 with castor 927. And my elevation I ride in varies from 900'-1400'. Any input would be awesome. I'm lost haha
AJ565 wrote:
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right? If you’ve done those things personally I would...
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right?

If you’ve done those things personally I would change to a different oil and run it 55:1 or 60:1 and see what happens. I’ve read about some having issues with 927.
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know how to set float height. Would the needle clip need to be down more than the 2 slot because of elevation? Idk what effect the changing of slots has. Coming from efi 4 strokes so I'm a noob to all of this. Trying to understand how it all works.
AJ565
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AJ565 5/29/2022 8:19pm
5/29/2022 8:19pm
etters312 wrote:
So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all...
So I followed the jetting you have here for my 2018 250sx. The one with the 5.5 slide. And the bike won't really run at all with the choke off. And with choke on it will half ass run but bogs down and shuts off. I run ethanol free 90 octane gas mixed 50:1 with castor 927. And my elevation I ride in varies from 900'-1400'. Any input would be awesome. I'm lost haha
AJ565 wrote:
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right? If you’ve done those things personally I would...
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right?

If you’ve done those things personally I would change to a different oil and run it 55:1 or 60:1 and see what happens. I’ve read about some having issues with 927.
etters312 wrote:
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know...
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know how to set float height. Would the needle clip need to be down more than the 2 slot because of elevation? Idk what effect the changing of slots has. Coming from efi 4 strokes so I'm a noob to all of this. Trying to understand how it all works.
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if it was my bike. The elevation shouldn’t be enough to mess with anything. I’m at 650’ so not too far off and there are guys running this jetting much higher and it’s been stable.
Mx451
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Mx451 5/30/2022 9:47am
5/30/2022 9:47am
AJ565 wrote:
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if...
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if it was my bike. The elevation shouldn’t be enough to mess with anything. I’m at 650’ so not too far off and there are guys running this jetting much higher and it’s been stable.
I'm at 4500' and running first page specs on a 2019 125sx. Runs perfect! Only other mods are PC pipe and silencer. Frankly i was shocked how well it worked this much higher. Thanks AJ!
FGR01
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FGR01 5/30/2022 2:15pm
5/30/2022 2:15pm
AJ565 wrote:
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if...
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if it was my bike. The elevation shouldn’t be enough to mess with anything. I’m at 650’ so not too far off and there are guys running this jetting much higher and it’s been stable.
Mx451 wrote:
I'm at 4500' and running first page specs on a 2019 125sx. Runs perfect! Only other mods are PC pipe and silencer. Frankly i was shocked...
I'm at 4500' and running first page specs on a 2019 125sx. Runs perfect! Only other mods are PC pipe and silencer. Frankly i was shocked how well it worked this much higher. Thanks AJ!
Yup, same here. On my TC125 I go from 600' to 5,000' with the jetting and don't really need to change for those elevations. I am actually slightly richer than the page-1 specs to account for running AvGas.

Pit Row

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etters312
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etters312 6/3/2022 3:14pm
6/3/2022 3:14pm
AJ565 wrote:
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right? If you’ve done those things personally I would...
You replaced everything listed yes? Did you replace the jet block gasket yet? Reeds good? Float height right?

If you’ve done those things personally I would change to a different oil and run it 55:1 or 60:1 and see what happens. I’ve read about some having issues with 927.
etters312 wrote:
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know...
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know how to set float height. Would the needle clip need to be down more than the 2 slot because of elevation? Idk what effect the changing of slots has. Coming from efi 4 strokes so I'm a noob to all of this. Trying to understand how it all works.
AJ565 wrote:
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if...
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if it was my bike. The elevation shouldn’t be enough to mess with anything. I’m at 650’ so not too far off and there are guys running this jetting much higher and it’s been stable.
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched and wasn't sealing completely and dumping fuel out the overflow . Replaced that. Put it back together. Fired up first kick. Had to adjust my air screw in to 1/2 a turn out to get it right and not falling on its face off the start but it's running amazing now. Thank you for all of your help and specs!
jcp411
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Denton, TX, USA
jcp411 6/4/2022 1:01pm
6/4/2022 1:01pm
Well i got the mikuni working with some help.
2022 KTM 125xc
#5 slide
32.5 pj
42-71 needle 3rd clip
490 main
S4 needle jet
90-100 degrees 600ft
Bike runs great no off idle bog
Then the temps dropped to the 70’s and it ran like crap!
Pulled the mikuni off the bike and installed a keihin air striker 38 and with some help getting the jetting dailed in its sooo much better in every way. Very crisp!
1
etters312
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Karthaus, PA, USA
etters312 6/5/2022 8:17am
6/5/2022 8:17am
etters312 wrote:
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know...
I replaced everything listed with your recommendations. Did not replace jet block gasket. Reeds are good, no chips or cracks. They look perfect. I dont know how to set float height. Would the needle clip need to be down more than the 2 slot because of elevation? Idk what effect the changing of slots has. Coming from efi 4 strokes so I'm a noob to all of this. Trying to understand how it all works.
AJ565 wrote:
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if...
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if it was my bike. The elevation shouldn’t be enough to mess with anything. I’m at 650’ so not too far off and there are guys running this jetting much higher and it’s been stable.
etters312 wrote:
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched...
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched and wasn't sealing completely and dumping fuel out the overflow . Replaced that. Put it back together. Fired up first kick. Had to adjust my air screw in to 1/2 a turn out to get it right and not falling on its face off the start but it's running amazing now. Thank you for all of your help and specs!
I'm getting a TON of smoke. I'm thinking switching back to 60:1 from 50:1
Tuplavee
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FI
Tuplavee 6/5/2022 11:09am
6/5/2022 11:09am
My Tc250 is actually running quite fine with
4.0 slide / 43-73 / 3rd clip / PJ 37,5 / MJ 460 / 50:1 / 8mm float level / looped overflow / air screw 2,75 turns out (I know, should be less). Plug color is quite light.

Thinking that if I should even cancel my back ordered 5.5 slide, could it be better?
AJ565
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AJ565 6/5/2022 4:38pm
6/5/2022 4:38pm
AJ565 wrote:
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if...
Replace the gasket and see how it runs. That gasket is a known fail point and will make it run funny. That’s where I’d start if it was my bike. The elevation shouldn’t be enough to mess with anything. I’m at 650’ so not too far off and there are guys running this jetting much higher and it’s been stable.
etters312 wrote:
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched...
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched and wasn't sealing completely and dumping fuel out the overflow . Replaced that. Put it back together. Fired up first kick. Had to adjust my air screw in to 1/2 a turn out to get it right and not falling on its face off the start but it's running amazing now. Thank you for all of your help and specs!
etters312 wrote:
I'm getting a TON of smoke. I'm thinking switching back to 60:1 from 50:1
Drop the needle one clip.
AJ565
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AJ565 6/5/2022 4:39pm
6/5/2022 4:39pm
Tuplavee wrote:
My Tc250 is actually running quite fine with 4.0 slide / 43-73 / 3rd clip / PJ 37,5 / MJ 460 / 50:1 / 8mm float...
My Tc250 is actually running quite fine with
4.0 slide / 43-73 / 3rd clip / PJ 37,5 / MJ 460 / 50:1 / 8mm float level / looped overflow / air screw 2,75 turns out (I know, should be less). Plug color is quite light.

Thinking that if I should even cancel my back ordered 5.5 slide, could it be better?
It’s way better. Hopefully someone else that’s tried to keep stock and switched it up so it’s not just me saying that.
1
oldslownewb
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Ontario, CA
oldslownewb 6/5/2022 6:32pm
6/5/2022 6:32pm
AJ565 wrote:
It’s way better. Hopefully someone else that’s tried to keep stock and switched it up so it’s not just me saying that.
The top end is way better, just keeps pulling longer compared to stock. On the track I think that would make a huge difference in how long you can pull a gear. Before it was all mid range nothing up top. For me I ride woods and the consistency is way better which for me was the biggest thing. Never knew how it would run before. A 5c temp change would throw it off. Now can pretty much ride all season with just turning air screw.
Mx451
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Bozeman, MT, USA
Mx451 6/6/2022 4:36am
6/6/2022 4:36am
AJ565 wrote:
It’s way better. Hopefully someone else that’s tried to keep stock and switched it up so it’s not just me saying that.
22 Tc250 owner here. When i switched everything out it was like a whole new bike. Pulled harder everywhere, was much more crisp, and more stable across varying atmospheric conditions. Like going from a stock to a mod bike.
crawfishoo 6/6/2022 6:28am
6/6/2022 6:28am
If anyone if interested in trying this jetting setup I have a kit available in the For Sale/Bazaar forum. I sold my 18 250SX and used this jetting setup for about 20 hrs. All the comments are spot on, it really cleans up the bottom end and better transition into a more usable top end power.
etters312
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etters312 6/10/2022 8:34pm
6/10/2022 8:34pm
etters312 wrote:
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched...
So... I took it all back apart. My float height was way off somehow. I got that set. Also my float valve o-ring had gotten pinched and wasn't sealing completely and dumping fuel out the overflow . Replaced that. Put it back together. Fired up first kick. Had to adjust my air screw in to 1/2 a turn out to get it right and not falling on its face off the start but it's running amazing now. Thank you for all of your help and specs!
etters312 wrote:
I'm getting a TON of smoke. I'm thinking switching back to 60:1 from 50:1
AJ565 wrote:
Drop the needle one clip.
I dropped the needle down to the 1 position for the clip. Still lots of smoke. Bog off idle like to start moving. If I turn the air screw in the whole way it doesn't bog but still lots of smoke. I'm going to switch from Castor 927 to Amsoil dominator. Would you think I'd need to change my mix ratio or my pilot jet size also? Needle with clip in the 1 position and air screw all the way in would be leaning out my pilot correct?
FGR01
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FGR01 6/10/2022 8:50pm
6/10/2022 8:50pm
etters312 wrote:
I'm getting a TON of smoke. I'm thinking switching back to 60:1 from 50:1
AJ565 wrote:
Drop the needle one clip.
etters312 wrote:
I dropped the needle down to the 1 position for the clip. Still lots of smoke. Bog off idle like to start moving. If I turn...
I dropped the needle down to the 1 position for the clip. Still lots of smoke. Bog off idle like to start moving. If I turn the air screw in the whole way it doesn't bog but still lots of smoke. I'm going to switch from Castor 927 to Amsoil dominator. Would you think I'd need to change my mix ratio or my pilot jet size also? Needle with clip in the 1 position and air screw all the way in would be leaning out my pilot correct?
Air screw all the way in is completely closing off the air passage way. Max rich. Try going the other way. Start at 1.5 open and work more open in 1/4 turn increments blipping the throttle until you get best/clean response. If you need to go more than 2.25 turns open it's time to start thinking about a leaner pilot.

yeah, I agree with getting rid of the 927 and copying AJ's oil and ratio.
etters312
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etters312 6/11/2022 2:33pm
6/11/2022 2:33pm
AJ565 wrote:
Drop the needle one clip.
etters312 wrote:
I dropped the needle down to the 1 position for the clip. Still lots of smoke. Bog off idle like to start moving. If I turn...
I dropped the needle down to the 1 position for the clip. Still lots of smoke. Bog off idle like to start moving. If I turn the air screw in the whole way it doesn't bog but still lots of smoke. I'm going to switch from Castor 927 to Amsoil dominator. Would you think I'd need to change my mix ratio or my pilot jet size also? Needle with clip in the 1 position and air screw all the way in would be leaning out my pilot correct?
FGR01 wrote:
Air screw all the way in is completely closing off the air passage way. Max rich. Try going the other way. Start at 1.5 open and...
Air screw all the way in is completely closing off the air passage way. Max rich. Try going the other way. Start at 1.5 open and work more open in 1/4 turn increments blipping the throttle until you get best/clean response. If you need to go more than 2.25 turns open it's time to start thinking about a leaner pilot.

yeah, I agree with getting rid of the 927 and copying AJ's oil and ratio.
Turning screw out made it worse so I guess I'm too lean. I moved needle clip to 3 spot. (3rd down from the top) and It works decent with the screw at 1.0 turns out. Might try to move clip to the 4 position and see if it runs and cleaner. It's still not very crisp right at the bottom.

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