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

dsk360
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dsk360 6/8/2021 6:19am
6/8/2021 6:19am
dsk360 wrote:
Hey AJ I've been following this thread for awhile and first off want to say thank you for all the great info. I've made quite a...
Hey AJ I've been following this thread for awhile and first off want to say thank you for all the great info. I've made quite a few changes to my jetting based on what I read here. Currently I'm sitting at 42-71 needle in the 2nd clip, pilot 30, main 480, and the air screw at 2 out. I did switch to the #5 slide that I notched. I run ethanol free gas and ride at about 700 feet above sea level in Michigan. Last weekend it was in the high 80s. After a tight woods section the bike would bobble when I got out for a second or two then clean up and run good. Am I to lean? Or what should I change to help this? It also seemed like it loaded up at the gas stop and took about 200 yards to clean up and run good again.
AJ565 wrote:
What bike? That’s the wrong needle for sure and is more then likely your problem. They seem pretty picky on having the wrong needle in it...
What bike? That’s the wrong needle for sure and is more then likely your problem. They seem pretty picky on having the wrong needle in it and even a half clip position makes a big difference.
It's a 19 150sx. I have also already done the jet block gasket. What needle should I try?
digger
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digger 6/8/2021 6:51am
6/8/2021 6:51am
dsk360 wrote:
Hey AJ I've been following this thread for awhile and first off want to say thank you for all the great info. I've made quite a...
Hey AJ I've been following this thread for awhile and first off want to say thank you for all the great info. I've made quite a few changes to my jetting based on what I read here. Currently I'm sitting at 42-71 needle in the 2nd clip, pilot 30, main 480, and the air screw at 2 out. I did switch to the #5 slide that I notched. I run ethanol free gas and ride at about 700 feet above sea level in Michigan. Last weekend it was in the high 80s. After a tight woods section the bike would bobble when I got out for a second or two then clean up and run good. Am I to lean? Or what should I change to help this? It also seemed like it loaded up at the gas stop and took about 200 yards to clean up and run good again.
AJ565 wrote:
What bike? That’s the wrong needle for sure and is more then likely your problem. They seem pretty picky on having the wrong needle in it...
What bike? That’s the wrong needle for sure and is more then likely your problem. They seem pretty picky on having the wrong needle in it and even a half clip position makes a big difference.
dsk360 wrote:
It's a 19 150sx. I have also already done the jet block gasket. What needle should I try?
You have a couple of issues going on there. That bike, I believe comes with an S-1 needle jet. It needs to be changed to a richer S-4 needle jet. The jet needle also has a starting diameter, 71 , that is too rich for that bike. That bike needs a needle with a 74 starting diameter.

The jetting combinations for these bikes that we have listed in this thread really need to be used as a kit. They don't run nearly as well as they could when you piece them together one part at a time

For your sx150, I would start off with:

Jet needle--42-74 in the #2 clip position

Pilot---30

Needle jet----S-4

Main---490

Slide--5.0

Air screw----2.0

float level----8.0 mm

It sounds like you have already replaced the jet block gasket.
dsk360
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dsk360 6/8/2021 7:56am
6/8/2021 7:56am
AJ565 wrote:
What bike? That’s the wrong needle for sure and is more then likely your problem. They seem pretty picky on having the wrong needle in it...
What bike? That’s the wrong needle for sure and is more then likely your problem. They seem pretty picky on having the wrong needle in it and even a half clip position makes a big difference.
dsk360 wrote:
It's a 19 150sx. I have also already done the jet block gasket. What needle should I try?
digger wrote:
You have a couple of issues going on there. That bike, I believe comes with an S-1 needle jet. It needs to be changed to a...
You have a couple of issues going on there. That bike, I believe comes with an S-1 needle jet. It needs to be changed to a richer S-4 needle jet. The jet needle also has a starting diameter, 71 , that is too rich for that bike. That bike needs a needle with a 74 starting diameter.

The jetting combinations for these bikes that we have listed in this thread really need to be used as a kit. They don't run nearly as well as they could when you piece them together one part at a time

For your sx150, I would start off with:

Jet needle--42-74 in the #2 clip position

Pilot---30

Needle jet----S-4

Main---490

Slide--5.0

Air screw----2.0

float level----8.0 mm

It sounds like you have already replaced the jet block gasket.
Thanks Digger. Those settings work with the notched #5 slide correct?
digger
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digger 6/8/2021 8:41am
6/8/2021 8:41am
dsk360 wrote:
Thanks Digger. Those settings work with the notched #5 slide correct?
Yes, you may possibly need to use a 27.5 pilot in the heat, depending on how large of a notch you made.
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dsk360
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dsk360 6/8/2021 9:09am
6/8/2021 9:09am
dsk360 wrote:
Thanks Digger. Those settings work with the notched #5 slide correct?
digger wrote:
Yes, you may possibly need to use a 27.5 pilot in the heat, depending on how large of a notch you made.
I followed the directions you gave earlier in the thread so about 3mm
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AJ565
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AJ565 6/8/2021 7:41pm
6/8/2021 7:41pm
digger wrote:
You have a couple of issues going on there. That bike, I believe comes with an S-1 needle jet. It needs to be changed to a...
You have a couple of issues going on there. That bike, I believe comes with an S-1 needle jet. It needs to be changed to a richer S-4 needle jet. The jet needle also has a starting diameter, 71 , that is too rich for that bike. That bike needs a needle with a 74 starting diameter.

The jetting combinations for these bikes that we have listed in this thread really need to be used as a kit. They don't run nearly as well as they could when you piece them together one part at a time

For your sx150, I would start off with:

Jet needle--42-74 in the #2 clip position

Pilot---30

Needle jet----S-4

Main---490

Slide--5.0

Air screw----2.0

float level----8.0 mm

It sounds like you have already replaced the jet block gasket.
I echo this, do all of it before asking why it’s still not right because you’ve only done some of the changes. With diggers guidance pointing me in the right direction we’ve got a really solid baseline for all the bikes that requires very minor tweaks for a lot of temps and elevations.
dsk360
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dsk360 6/9/2021 3:55am
6/9/2021 3:55am
AJ565 wrote:
I echo this, do all of it before asking why it’s still not right because you’ve only done some of the changes. With diggers guidance pointing...
I echo this, do all of it before asking why it’s still not right because you’ve only done some of the changes. With diggers guidance pointing me in the right direction we’ve got a really solid baseline for all the bikes that requires very minor tweaks for a lot of temps and elevations.
I started at the settings in the first post. And playing with different settings led me to where it is today. I'm gonna go back to those settings and see how it runs again. Thanks again for the help
RH101
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RH101 6/11/2021 2:49pm
6/11/2021 2:49pm
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally sorted my 19 150sx, it was boggy rich in that 1/3 throttle zone from the day I picked it up from the dealer.. Anyway I have one thing more to add, for the past 30hrs I have been using the KTM iridium spark plug and yesterday I changed back to the stock plug and I have to say it runs better. Even with all of the carb mods done as suggested I would find some very minor spluttering around 1/3 throttle if I was riding enduro (I do 90% MX) and it was low rpm on/off throttle riding and then it would open into a straight. That initial wide open crack of the throttle would still give some bog. Anyway yesterday I threw the old stock plug back into it, not even a new plug btw and all of that was gone. It may be worth trying for anyone else having the same issue. Thanks again for the tips!
huckster mcplush 6/11/2021 3:47pm
6/11/2021 3:47pm
RH101 wrote:
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally...
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally sorted my 19 150sx, it was boggy rich in that 1/3 throttle zone from the day I picked it up from the dealer.. Anyway I have one thing more to add, for the past 30hrs I have been using the KTM iridium spark plug and yesterday I changed back to the stock plug and I have to say it runs better. Even with all of the carb mods done as suggested I would find some very minor spluttering around 1/3 throttle if I was riding enduro (I do 90% MX) and it was low rpm on/off throttle riding and then it would open into a straight. That initial wide open crack of the throttle would still give some bog. Anyway yesterday I threw the old stock plug back into it, not even a new plug btw and all of that was gone. It may be worth trying for anyone else having the same issue. Thanks again for the tips!
Do you by chance have both plug numbers for reference? Thanks :-)
RH101
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RH101 6/11/2021 4:17pm
6/11/2021 4:17pm
RH101 wrote:
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally...
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally sorted my 19 150sx, it was boggy rich in that 1/3 throttle zone from the day I picked it up from the dealer.. Anyway I have one thing more to add, for the past 30hrs I have been using the KTM iridium spark plug and yesterday I changed back to the stock plug and I have to say it runs better. Even with all of the carb mods done as suggested I would find some very minor spluttering around 1/3 throttle if I was riding enduro (I do 90% MX) and it was low rpm on/off throttle riding and then it would open into a straight. That initial wide open crack of the throttle would still give some bog. Anyway yesterday I threw the old stock plug back into it, not even a new plug btw and all of that was gone. It may be worth trying for anyone else having the same issue. Thanks again for the tips!
huckster mcplush wrote:
Do you by chance have both plug numbers for reference? Thanks :-)
Yeah the stock plug is an NGK BR9ECM and the iridium KTM Race parts plug is a BR9ECMIX
huckster mcplush 6/11/2021 4:29pm
6/11/2021 4:29pm
RH101 wrote:
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally...
I have been a longtime silent follower of this thread and I have to say a personal thanks to AJ and Digger, your suggestions have totally sorted my 19 150sx, it was boggy rich in that 1/3 throttle zone from the day I picked it up from the dealer.. Anyway I have one thing more to add, for the past 30hrs I have been using the KTM iridium spark plug and yesterday I changed back to the stock plug and I have to say it runs better. Even with all of the carb mods done as suggested I would find some very minor spluttering around 1/3 throttle if I was riding enduro (I do 90% MX) and it was low rpm on/off throttle riding and then it would open into a straight. That initial wide open crack of the throttle would still give some bog. Anyway yesterday I threw the old stock plug back into it, not even a new plug btw and all of that was gone. It may be worth trying for anyone else having the same issue. Thanks again for the tips!
huckster mcplush wrote:
Do you by chance have both plug numbers for reference? Thanks :-)
RH101 wrote:
Yeah the stock plug is an NGK BR9ECM and the iridium KTM Race parts plug is a BR9ECMIX
Okay cool so you are using both the iridium and standard versions of the shorter plug. Have you used the full size plug in the iridium by chance? I'm currently using the br9eix with the solid tip with good results. 17 150 xcw...
RH101
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RH101 6/11/2021 4:38pm
6/11/2021 4:38pm
No I haven't tried anything other than those two plugs. To be honest, after going back to the BR9ECM and getting such good results doubt I'll try anything else
RH101
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RH101 6/13/2021 3:03pm
6/13/2021 3:03pm
Correction, the iridium KTM poweparts plug I was running was the BR9ECMVX...
fredmotokx 6/14/2021 4:25pm
6/14/2021 4:25pm Edited Date/Time 6/14/2021 4:50pm
Hi guys,
A small update about the PV valve, went from stock adjustment to 1.75 turns in form unscrew made a significant change on the bottom end power, I should receive my 42-74 needle this week, this means we will cut my stock #4 slide into a #5.

My dad is a machinist he will help me cut it (or do it for me), I added comments on those pictures to helps us make it perfect.
Anything I am missing out on?


Credit to @digger for the picture

Credit to @swatdoc for the picture

Thank you
digger
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digger 6/14/2021 5:09pm
6/14/2021 5:09pm
The only thing that I'll add, is that I left it rough so that you could see where and what was cut. I use a small drum sander to smooth it out before I give them back.
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DuroTools
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DuroTools 6/14/2021 5:51pm
6/14/2021 5:51pm
digger wrote:
The only thing that I'll add, is that I left it rough so that you could see where and what was cut. I use a small...
The only thing that I'll add, is that I left it rough so that you could see where and what was cut. I use a small drum sander to smooth it out before I give them back.
Does the chain saw file mod make a huge difference? I did the big one but wanted to test it before doing the small one. Any benefit of leaving as is or should I do the small one asap?
DynoDan22
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DynoDan22 6/14/2021 6:50pm
6/14/2021 6:50pm
Anyone notice that the YZ125 Mikuni TMX-x has the slot already cut into it (chainsaw file cut)? I'm wondering why KTM or Honda didn't do this on their TMX-x slides.
Bruce372
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Bruce372 6/14/2021 8:02pm
6/14/2021 8:02pm
I would start by taking 0.5mm out of the slide if you are on 125 or 150.

I bought a proper oem #5 slide and it was lean.

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digger
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digger 6/14/2021 8:43pm
6/14/2021 8:43pm
DynoDan22 wrote:
Anyone notice that the YZ125 Mikuni TMX-x has the slot already cut into it (chainsaw file cut)? I'm wondering why KTM or Honda didn't do this...
Anyone notice that the YZ125 Mikuni TMX-x has the slot already cut into it (chainsaw file cut)? I'm wondering why KTM or Honda didn't do this on their TMX-x slides.
Those slides are different from each other in more ways than just the slide cut away. The Yamaha and KTM TMX-x slides cant be used in the Honda TMX-x without being modified. Not too mention that the Yamaha slide is a notched #4.25.
If I had to venture a guess as to why KTM and Honda spec'ed the Mikuni TMX-x carbs that they did, I think it has to do with cost. Each manufacture is specing a carb for 2/3 different displacement engines. The slide is the most expensive part in the carb and changing between each displacement would cost them xxx.

Duro, notching the slide is not super critical, but it does make the pilot circuit more efficient, which I find to be helpful.

Bruce, did you notch the oem #5.0 slide ? It richens up the first 1/4 throttle a little bit.
sandman768
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sandman768 6/16/2021 5:51am
6/16/2021 5:51am
Picking up a 22 125SX soon, anyone have one yet? How is they stock jetting? Thanks
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fredmotokx 6/16/2021 6:35am
6/16/2021 6:35am
sandman768 wrote:
Picking up a 22 125SX soon, anyone have one yet? How is they stock jetting? Thanks
Stock jetting is the same as years before, you will probably have to use the base jetting spec in the first thread to make it better.
fredmotokx 6/19/2021 2:19pm
6/19/2021 2:19pm
Hi guys,

Today I installed the 42-74 needle and #5 cut slide on my 2021 150sx (A little less than #5). Went for a ride around the block but it's hard to tell if there is an improvement from before.

I Will report in the next few days, we are going to the track tomorrow.

Here some pictures of the tools I used to cut my slide and the slide itself. Was pretty easy after all, as mentioned before, taking your time is the key. I used some polish compound last. Could not make the small dent under the arch back to a perfect, small mistake on my end.

Thanks for the thread, so much useful information.



1
fredmotokx 6/26/2021 6:16am
6/26/2021 6:16am
After 2 MX days with this jetting (The same one as the first post), I can definitively say the bike has way more bottom end, roll out of the corners way easier. No more bug going from 1/8 throttle to WOT.

I am thinking about switching back to stock 48T rear instead of the 50T I am currently using to use more the powerband and less gear shift.

Might also have to try a 27.5 PJ when temps will get hotter.

Stock 2021 150SX with open airbox cover
MJ 490
PJ 30
Needle Jet S4
AS 1.5
Slide about #4.8 with a 4mm width and 3mm deep groove
Needle 42-74 on the 2nd clip
Needle jet S4
PV 1.75 turns in from all the way out.
Fuel mix 40:1 Motorex 2T Crosspower
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AJ565
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AJ565 6/26/2021 9:49am
6/26/2021 9:49am
You might get away with a bigger main. These engines can handle tons of fuel up top it seems. Back to back same day testing with my 250 showed almost 2 mph difference between a 490 main and a 500 main on the same section tapped out in 3rd gear. for sure worth trying.
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fredmotokx 6/26/2021 12:37pm
6/26/2021 12:37pm
AJ565 wrote:
You might get away with a bigger main. These engines can handle tons of fuel up top it seems. Back to back same day testing with...
You might get away with a bigger main. These engines can handle tons of fuel up top it seems. Back to back same day testing with my 250 showed almost 2 mph difference between a 490 main and a 500 main on the same section tapped out in 3rd gear. for sure worth trying.
Yeah was thinking about this when temp will be a bit lower, might test it next time I hit the track too.
dwilli150
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dwilli150 6/27/2021 6:04am
6/27/2021 6:04am
Has anyone tried the FMF REV pipe on the 125/150?
FGR01
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FGR01 6/27/2021 7:37am
6/27/2021 7:37am
dwilli150 wrote:
Has anyone tried the FMF REV pipe on the 125/150?
I am currently running the FMF Factory Fatty and the normal length (not shorty) powercore silencer on my TC125. I really like this combo. I considered the Rev pipe but the way my bike screams on top now is almost frightening so I wasn't really sure I wanted it screaming any harder. Plus the bottom it has now is pretty impressive and comes in handy when I fail to carry enough momentum in a turn or use 3rd like I'm on a 450 Laughing
dwilli150
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dwilli150 6/27/2021 8:50am
6/27/2021 8:50am
dwilli150 wrote:
Has anyone tried the FMF REV pipe on the 125/150?
FGR01 wrote:
I am currently running the FMF Factory Fatty and the normal length (not shorty) powercore silencer on my TC125. I really like this combo. I considered...
I am currently running the FMF Factory Fatty and the normal length (not shorty) powercore silencer on my TC125. I really like this combo. I considered the Rev pipe but the way my bike screams on top now is almost frightening so I wasn't really sure I wanted it screaming any harder. Plus the bottom it has now is pretty impressive and comes in handy when I fail to carry enough momentum in a turn or use 3rd like I'm on a 450 Laughing
Nice!
Hammer 663s
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Hammer 663s 6/27/2021 11:03am
6/27/2021 11:03am
dwilli150 wrote:
Has anyone tried the FMF REV pipe on the 125/150?
How about a FMF Shorty on the stock pipe? Would expect a little more low/mid....

Hammer 663s
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sandman768
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sandman768 7/1/2021 6:05am
7/1/2021 6:05am Edited Date/Time 7/1/2021 6:07am
Hey guys, I am about to order the needed carb parts to try this jetting, regarding the 42-74 needle… does it have to be a Yamaha needle or is the Ktm 42-74 needle the same? Thanks

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