2017+ KTM 250SX gearing

dooher
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dooher
Edited Date/Time 11/26/2021 11:59pm
Hey guys, for those of you who ride and race a 2017+ KTM 250 SX, what's your preferred gearing setup? Stock (14/50), or going up or down on the rear, e.g. gear up with 49T to get a bit more top end, or gear it down w/ a 51T rear to get into 3rd gear sooner? Re: the motor is freakin' awesome and amazing, but it's definitely more of a low-mid motor...
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suspensionguy 11/16/2021 5:45pm
11/16/2021 5:45pm
For me it’s 14/48. Been on TC250’s and 250SX since 2015. West coast Offroad and Mx. KTM changed the stock gearing in 2020 to 14/49 FYI.
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dooher
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dooher 11/16/2021 5:52pm
11/16/2021 5:52pm
suspensionguy wrote:
For me it’s 14/48. Been on TC250’s and 250SX since 2015. West coast Offroad and Mx. KTM changed the stock gearing in 2020 to 14/49 FYI.
> KTM changed the stock gearing in 2020 to 14/49 FYI.

Ahh! Thanks for adding that info - was going to go down to a 49, and that would have been just replacing exactly what I have today. lol.
AJ565
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AJ565 11/16/2021 6:58pm
11/16/2021 6:58pm
14/52. It’s almost exactly the same as running a 13/49 (stock was 13/50), but the chain angles are different and let the rear suspension work better.
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AJ565
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AJ565 11/16/2021 7:00pm
11/16/2021 7:00pm
Also rejetting the bike fixes most of the top end pull so it’s a strong motor low to top.
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dooher
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dooher 11/16/2021 7:34pm
11/16/2021 7:34pm
AJ565 wrote:
Also rejetting the bike fixes most of the top end pull so it’s a strong motor low to top.
Yes, I 100% agree here, e.g. I've lately been running U4.4 at 60:1 w/ a 500 main with the needle in the 3rd position, and yeah, definitely runs much better on top.
seth505
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seth505 11/17/2021 8:01am
11/17/2021 8:01am
I liked it with stock gearing honestly (it's 14/50 rather than 13/50). That is with fixed jetting, HGS exhaust.
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YZed250
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YZed250 11/17/2021 11:34am
11/17/2021 11:34am
I used 13/47 on mine for mx style tracks and 14/47 off-road on 2017 250sx.
47T allowed me to switch gearing really easily bw MX and fast off-road.
Add a pipe/silencer, and good jetting and this bike likes to spin with stock gearing. The 2019+ got a longer swingarm which helped by being able to extend the wheelbase a little further.
With whatever gearing combo you arrive at, it's best to be able to run the axle in the middle to the back of the slots.
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dooher
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dooher 11/17/2021 12:19pm
11/17/2021 12:19pm
AJ565 wrote:
14/52. It’s almost exactly the same as running a 13/49 (stock was 13/50), but the chain angles are different and let the rear suspension work better.
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks all!
AJ565
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AJ565 11/17/2021 6:09pm
11/17/2021 6:09pm
AJ565 wrote:
14/52. It’s almost exactly the same as running a 13/49 (stock was 13/50), but the chain angles are different and let the rear suspension work better.
dooher wrote:
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks...
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks all!
Get into 3rd sooner? No. Pull longer in 2nd and 3rd? Yes. At the tracks around me stock gearing I was mainly 3, 4, 5 as 2nd was too short and the rest didn’t pull long enough. The 14/52 bridges the gap so the tracks are 2, 3, 4, BUT the longer pull means I wasn’t tapped out in more of the sections where by the time I upshifted I would be on the brakes. That extra 20-30’ of pull makes a huge difference.
opyguy
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opyguy 11/17/2021 7:31pm
11/17/2021 7:31pm
Stock gearing 14-49 on the 21’s
I have one, pull 3rd and 4th the entire track
even tight 180s… I will say second is useless
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dooher
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dooher 11/17/2021 8:10pm
11/17/2021 8:10pm
opyguy wrote:
Stock gearing 14-49 on the 21’s
I have one, pull 3rd and 4th the entire track
even tight 180s… I will say second is useless
Mine is a 2021 as well. Btw, these newer KTM 250 2 strokes are amazing ... I had a 2014, and this bike is like a factory bike in comparison.
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YZed250
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YZed250 11/18/2021 9:29am
11/18/2021 9:29am
AJ565 wrote:
14/52. It’s almost exactly the same as running a 13/49 (stock was 13/50), but the chain angles are different and let the rear suspension work better.
dooher wrote:
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks...
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks all!
AJ565 wrote:
Get into 3rd sooner? No. Pull longer in 2nd and 3rd? Yes. At the tracks around me stock gearing I was mainly 3, 4, 5 as...
Get into 3rd sooner? No. Pull longer in 2nd and 3rd? Yes. At the tracks around me stock gearing I was mainly 3, 4, 5 as 2nd was too short and the rest didn’t pull long enough. The 14/52 bridges the gap so the tracks are 2, 3, 4, BUT the longer pull means I wasn’t tapped out in more of the sections where by the time I upshifted I would be on the brakes. That extra 20-30’ of pull makes a huge difference.
AJ nailed it, again Laughing
2nd was too short and the rest didn't pull long enough

The combo of the short band with the short stock trans ratios mean its hard to find the perfect corner.
You have to go taller w the external gearing and look for more over-rev (pv, pipe, head, silencer) as well as extend the wheelbase.

You want to be able to initiate the corner exit corner at the bottom of the band, and drive all the way through the power without having to shift a couple times in the first 50ft.

That's just my 2c from racing west coast tracks which can be pretty dry/slick on the 2017. Granted, the bike has been developed and not everybody rides on these SoCal tracks.
crawfishoo 11/25/2021 8:29pm
11/25/2021 8:29pm
AJ565 wrote:
14/52. It’s almost exactly the same as running a 13/49 (stock was 13/50), but the chain angles are different and let the rear suspension work better.
dooher wrote:
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks...
Okay, so you like to get into 3rd gear sooner / make 3rd gear more useable. I think I need to try this direction first. Thanks all!
AJ565 wrote:
Get into 3rd sooner? No. Pull longer in 2nd and 3rd? Yes. At the tracks around me stock gearing I was mainly 3, 4, 5 as...
Get into 3rd sooner? No. Pull longer in 2nd and 3rd? Yes. At the tracks around me stock gearing I was mainly 3, 4, 5 as 2nd was too short and the rest didn’t pull long enough. The 14/52 bridges the gap so the tracks are 2, 3, 4, BUT the longer pull means I wasn’t tapped out in more of the sections where by the time I upshifted I would be on the brakes. That extra 20-30’ of pull makes a huge difference.
Looking to add some clarification. The 17+ 250SX comes stock with a 14 tooth front, the XC has a 13 front but not the SX. Are you using a 15/52 combo? Going 14/52 would gear the bike down and make 1st and 2nd very short.

I run 14/49 and do like it. Even at 14/49 I rarely use 2nd gear, only in very tight hair pin turns. I might try 14/48 with my next set of chain and sprockets.
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AJ565
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AJ565 11/25/2021 9:47pm
11/25/2021 9:47pm
crawfishoo wrote:
Looking to add some clarification. The 17+ 250SX comes stock with a 14 tooth front, the XC has a 13 front but not the SX. Are...
Looking to add some clarification. The 17+ 250SX comes stock with a 14 tooth front, the XC has a 13 front but not the SX. Are you using a 15/52 combo? Going 14/52 would gear the bike down and make 1st and 2nd very short.

I run 14/49 and do like it. Even at 14/49 I rarely use 2nd gear, only in very tight hair pin turns. I might try 14/48 with my next set of chain and sprockets.
No, the 17-20(I think it’s 20) 250sx comes stock with 13/50 gearing. 21+ they come with a 14 front.
crawfishoo 11/26/2021 6:11am
11/26/2021 6:11am
Not trying to be rude, looking to help you out here. Go look at your manual and a parts phish. All 17+ 250sx come with a 14 tooth front. That is why several post have asked you about gearing it down, you are recommending and suggesting to increase the drive ratio but in reality your 14/52 is lower than stock.
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AJ565
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AJ565 11/26/2021 9:13am
11/26/2021 9:13am
crawfishoo wrote:
Not trying to be rude, looking to help you out here. Go look at your manual and a parts phish. All 17+ 250sx come with a...
Not trying to be rude, looking to help you out here. Go look at your manual and a parts phish. All 17+ 250sx come with a 14 tooth front. That is why several post have asked you about gearing it down, you are recommending and suggesting to increase the drive ratio but in reality your 14/52 is lower than stock.
That’s really interesting. I did look it up and yes it shows 14/50 stock. The interesting part for me is I know I took off a 13 front on my bike because I counted the teeth when I ordered a replacement and even the picture of the bike in the manual has a 13 front on the SX. Now I have to go see if I have the 49 rear still so I can give that a try.

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crawfishoo 11/26/2021 10:26am
11/26/2021 10:26am
No problem. The picture in the manual is not a 250/300 engine. Notice the sprocket is held in place with a circlip, that's just a generic photo likely from a 125.

Did you buy your bike used? For sure it would have come from the factory with a 14 tooth front.

Will be curious to hear your thoughts about a 52 vs 49 rear. Currently I can pull 3rd gear on the majority of tracks I ride. Longer straights I shift to 4th, but not often. I think if I went any taller I would have to start abusing the clutch through corners. If I keep good momentum I can roll on the throttle and not use any clutch in 3rd gear.
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jeffoff
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jeffoff 11/26/2021 10:27am
11/26/2021 10:27am
On my sand tyre set using 14/50.
Hard pack set 14/49 but thinking to try 48 to tame it more down.

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AJ565
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AJ565 11/26/2021 12:29pm
11/26/2021 12:29pm
crawfishoo wrote:
No problem. The picture in the manual is not a 250/300 engine. Notice the sprocket is held in place with a circlip, that's just a generic...
No problem. The picture in the manual is not a 250/300 engine. Notice the sprocket is held in place with a circlip, that's just a generic photo likely from a 125.

Did you buy your bike used? For sure it would have come from the factory with a 14 tooth front.

Will be curious to hear your thoughts about a 52 vs 49 rear. Currently I can pull 3rd gear on the majority of tracks I ride. Longer straights I shift to 4th, but not often. I think if I went any taller I would have to start abusing the clutch through corners. If I keep good momentum I can roll on the throttle and not use any clutch in 3rd gear.
Ahh good catch. No, I bought the bike new off the show room floor.

As for the gearing every track I’ve had it on the 14/52 has been perfect for. 2/3/4 on every track (we have some fast sections that are in the 58-59mph range so 4th is a must use at every track). I’m wondering if dropping to a 49 I’ll have to abuse the clutch. 3.71 vs. 3.5 ratio difference is a pretty good jump.
jeffoff
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jeffoff 11/26/2021 11:59pm
11/26/2021 11:59pm
Mine is not stock but last time out with the 49 on hardpack it lifted the front with every blip of the throttle, switched to less agressive map to make it bit more user friendly.
Some turns were taken in third, then i used to blip the clutch sometimes to spool up the rear.
Only used gear 2 / 3 , hit close to 70km/h on gps. Track with plenty turns, around 2min laptimes.

I like it as how it lengtened the gears for less shifting, and provide more traction (lessen wheelspin) for my 80kg frame.
All will depend on rider preference and track layout / soil.
On the sandtracks we have here i prefer the 50 with the paddle tyre.
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txorrider 2/14/2022 8:42am
2/14/2022 8:42am
crawfishoo wrote:
No problem. The picture in the manual is not a 250/300 engine. Notice the sprocket is held in place with a circlip, that's just a generic...
No problem. The picture in the manual is not a 250/300 engine. Notice the sprocket is held in place with a circlip, that's just a generic photo likely from a 125.

Did you buy your bike used? For sure it would have come from the factory with a 14 tooth front.

Will be curious to hear your thoughts about a 52 vs 49 rear. Currently I can pull 3rd gear on the majority of tracks I ride. Longer straights I shift to 4th, but not often. I think if I went any taller I would have to start abusing the clutch through corners. If I keep good momentum I can roll on the throttle and not use any clutch in 3rd gear.
AJ565 wrote:
Ahh good catch. No, I bought the bike new off the show room floor. As for the gearing every track I’ve had it on the 14/52...
Ahh good catch. No, I bought the bike new off the show room floor.

As for the gearing every track I’ve had it on the 14/52 has been perfect for. 2/3/4 on every track (we have some fast sections that are in the 58-59mph range so 4th is a must use at every track). I’m wondering if dropping to a 49 I’ll have to abuse the clutch. 3.71 vs. 3.5 ratio difference is a pretty good jump.
Sorry for the later contribution, my hunt/search was to find if anyone has tried the 14/47t combo particularly for off-road and I stumbled across this thread.

The newer bikes 20+ are 14/49...my '19' TC250 Husky was 14/50t stock-new with 116 link chain, (oem says 118 which is incorrect)...that gearing (with SX Head/CDI) is pretty much useless in the woods or if one is immortal. I've tested this bike with various head/cdi combos. For those that are into trails or harescramble/enduro events, these carbed TC/SX bikes are easy and badass lightweight woods racers, with some pretty easy mods.

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jg791
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jg791 9/2/2025 5:41pm
9/2/2025 5:41pm
AJ565 wrote:
14/52. It’s almost exactly the same as running a 13/49 (stock was 13/50), but the chain angles are different and let the rear suspension work better.

2023 GasGas MC 250 Carbed bike. Stock the bike is 14/49, changed it to 14/52 with a nice Renthal rear sprocket and this was the ticket. With good jetting/setup the bike feels perfect. 14/49 felt too tall to me. Thanks for the tip.

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FGR01 9/3/2025 5:42am
9/3/2025 5:42am
jg791 wrote:
2023 GasGas MC 250 Carbed bike. Stock the bike is 14/49, changed it to 14/52 with a nice Renthal rear sprocket and this was the ticket...

2023 GasGas MC 250 Carbed bike. Stock the bike is 14/49, changed it to 14/52 with a nice Renthal rear sprocket and this was the ticket. With good jetting/setup the bike feels perfect. 14/49 felt too tall to me. Thanks for the tip.

I have the same bike and I'm still running the 14/49.  My bike is a 300 now but even as a 250 I was running that gearing.  And I still almost never use 2nd in corners.  I tend to stay in 3rd and keep momentum up and sweep corners instead of trying to slow hard and accelerate hard.   Have you rejetted with the settings from the long thread?  For sure the best thing you can do to the bike to widen out the powerband and get some overrev.

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