2018 KTM SX250 PV opening rpm

ar15
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ar15
Edited Date/Time 8/2/2022 10:25pm
I found a discrepency between the Repair Manual and the User Manual of our 2018 KTM SX250. For the "Exhaust valve, beginning of adjustment" the User Manual says 5125 rpm, while the repair manual says 5500 rpm.

Which one is correct?
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FahQ
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FahQ 7/31/2022 4:22pm
7/31/2022 4:22pm
Depends on which spring and how much preload.
What are you trying to do?
ar15
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ar15 8/1/2022 12:40am
8/1/2022 12:40am
I just want to check/adjust the preload acc. to factory default setting. BTW, the rpm at which the PV opens is not dependent on what auxiliary spring (red/yellow/green) is used.
swordfish
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swordfish 8/1/2022 4:15am
8/1/2022 4:15am
5125.
On the XC and XCW it’s supposed to be 5k rpm.
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Not-a-Fan
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Not-a-Fan 8/1/2022 5:41am
8/1/2022 5:41am Edited Date/Time 8/1/2022 6:13am
Edited original post as it read weird

Where does your info come from swordfish? Are you a ktm tech?

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FGR01
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FGR01 8/1/2022 6:18am
8/1/2022 6:18am
ar15 wrote:
I just want to check/adjust the preload acc. to factory default setting. BTW, the rpm at which the PV opens is not dependent on what auxiliary...
I just want to check/adjust the preload acc. to factory default setting. BTW, the rpm at which the PV opens is not dependent on what auxiliary spring (red/yellow/green) is used.
"the rpm at which the PV opens is not dependent on what auxiliary spring (red/yellow/green) is used"

Tell us more.....
AJ565
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AJ565 8/1/2022 7:49am
8/1/2022 7:49am
ar15 wrote:
I just want to check/adjust the preload acc. to factory default setting. BTW, the rpm at which the PV opens is not dependent on what auxiliary...
I just want to check/adjust the preload acc. to factory default setting. BTW, the rpm at which the PV opens is not dependent on what auxiliary spring (red/yellow/green) is used.
FGR01 wrote:
"the rpm at which the PV opens is not dependent on what auxiliary spring (red/yellow/green) is used"

Tell us more.....
Right?

Also jetting plays into this as well and the preload effects jetting.
Not-a-Fan
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Not-a-Fan 8/1/2022 9:37am
8/1/2022 9:37am Edited Date/Time 8/1/2022 9:39am
He's right. The auxiliary springs don't effect the opening rpm. The preload on the main spring effects opening rpm and the auxiliary spring spring rate effects the speed at which it continues to open after the rpms are high enough to overcome the main spring in the pv system. That's why ktm tells you not to mess with the dial, you're messing up the initial timing on the low end, your shifting the entire performance box out of its designed range.
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Not-a-Fan
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Not-a-Fan 8/1/2022 9:41am
8/1/2022 9:41am
Imagine a progressively wound shock spring. Same concept but ktm does it with 2 springs for tunability.
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FGR01 8/1/2022 2:47pm
8/1/2022 2:47pm
I'm skeptical that 2 springs mounted as a pair on the same mechanism, and both controlled by the same preload adjuster, how one could magically control timing of opening and the other control speed of opening, while both simultaneously not affecting the performance of the other in it's respective job.

I could maybe see where each has a larger or smaller effect on rpm or rate of opening, but I think there would have to be some overlap. If someone has some real data, like you actually ran the bike on a dyno and tried all the combos of springs while monitoring the PV, I'm open to see it.
swordfish
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swordfish 8/1/2022 3:10pm
8/1/2022 3:10pm
Not-a-Fan wrote:
Edited original post as it read weird

Where does your info come from swordfish? Are you a ktm tech?
Sorry I typed the incorrect number. It’s 5500.
I’m not a tech, just know some dealers and techs as well as tuners.
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Not-a-Fan
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Not-a-Fan 8/1/2022 4:56pm
8/1/2022 4:56pm
Not-a-Fan wrote:
Edited original post as it read weird

Where does your info come from swordfish? Are you a ktm tech?
swordfish wrote:
Sorry I typed the incorrect number. It’s 5500.
I’m not a tech, just know some dealers and techs as well as tuners.
Thats awesome. Do you know if the xc is still 5k like you said or is that also 5500? Also do you know how quickly each spring allows the valve to open? Like red = starts 5.5k, ends 6k, yellow starts 5.5k, ends 6.5k etc etc?

I need to check a parts diagram, If the xc is 5k and sx is 55 I wonder if the xc uses a different main spring or if its just a preload adjustment on the dolly screw. I would think a preload adjustment would save them a ton of money vs a different spring.

swordfish
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swordfish 8/2/2022 4:34am
8/2/2022 4:34am
Not-a-Fan wrote:
Edited original post as it read weird

Where does your info come from swordfish? Are you a ktm tech?
swordfish wrote:
Sorry I typed the incorrect number. It’s 5500.
I’m not a tech, just know some dealers and techs as well as tuners.
Not-a-Fan wrote:
Thats awesome. Do you know if the xc is still 5k like you said or is that also 5500? Also do you know how quickly each...
Thats awesome. Do you know if the xc is still 5k like you said or is that also 5500? Also do you know how quickly each spring allows the valve to open? Like red = starts 5.5k, ends 6k, yellow starts 5.5k, ends 6.5k etc etc?

I need to check a parts diagram, If the xc is 5k and sx is 55 I wonder if the xc uses a different main spring or if its just a preload adjustment on the dolly screw. I would think a preload adjustment would save them a ton of money vs a different spring.

I believe XC, XCW and SX are all set for 5500. Quite a few TPi bikes come with the setting all over the place. JD Jetting has a ton of info you are looking for. Lots of dyno overlays with different springs and PV setting.
Here is an example.
swordfish
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swordfish 8/2/2022 4:36am
8/2/2022 4:36am Edited Date/Time 8/2/2022 4:41am
Not-a-Fan wrote:
Edited original post as it read weird

Where does your info come from swordfish? Are you a ktm tech?
swordfish wrote:
Sorry I typed the incorrect number. It’s 5500.
I’m not a tech, just know some dealers and techs as well as tuners.
Not-a-Fan wrote:
Thats awesome. Do you know if the xc is still 5k like you said or is that also 5500? Also do you know how quickly each...
Thats awesome. Do you know if the xc is still 5k like you said or is that also 5500? Also do you know how quickly each spring allows the valve to open? Like red = starts 5.5k, ends 6k, yellow starts 5.5k, ends 6.5k etc etc?

I need to check a parts diagram, If the xc is 5k and sx is 55 I wonder if the xc uses a different main spring or if its just a preload adjustment on the dolly screw. I would think a preload adjustment would save them a ton of money vs a different spring.

Just the dolly screw.
One full turn of the adjuster is aprox 150rpm.
https://jdjetting.com/ktm-power-valve-opening-vs-rpm-with-springs-and-d…
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swordfish
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swordfish 8/2/2022 4:53am
8/2/2022 4:53am Edited Date/Time 8/2/2022 6:03am
FGR01 wrote:
I'm skeptical that 2 springs mounted as a pair on the same mechanism, and both controlled by the same preload adjuster, how one could magically control...
I'm skeptical that 2 springs mounted as a pair on the same mechanism, and both controlled by the same preload adjuster, how one could magically control timing of opening and the other control speed of opening, while both simultaneously not affecting the performance of the other in it's respective job.

I could maybe see where each has a larger or smaller effect on rpm or rate of opening, but I think there would have to be some overlap. If someone has some real data, like you actually ran the bike on a dyno and tried all the combos of springs while monitoring the PV, I'm open to see it.
See pic and link above.
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Not-a-Fan
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Not-a-Fan 8/2/2022 8:22am
8/2/2022 8:22am Edited Date/Time 8/2/2022 8:31am
Is he saying the preset factory setting is wrong usually? Seems like the article is cut off Sad

Seems on one of the pics in the PV section where is he comparing red spring with different dolly positions, the absolute best most linear delivery setting was screw flush with the case. Seems to me I've been running my pv wrong for years by trusting ktm to set up the motor correctly. Against my instinct to trust the engineers im gonan try my dolly flush next time.


Not-a-Fan
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Not-a-Fan 8/2/2022 8:39am
8/2/2022 8:39am Edited Date/Time 8/2/2022 9:03am
Found the RPM data. Very cool. This is for an earlier generation though. JD days the aux spring only comes i to play once at the 5600 range. So i guess its not really progressive like I thought but its just a complete nonfactor actually? And jd says it starts at 5600 regardless of the dolly screw, but the pics above looks like it does extend the range. I guess I don't know what to think now.

Nvm i get it now. You can change the start of the opening but no matter where you put the dolly the aux spring is a non factor until 5600, even if the valve starts opening sooner because of the preload. So basically a dolly and aux spring combo that is too far off will really mess the powerband up during that transition phase.


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swordfish
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swordfish 8/2/2022 8:48am
8/2/2022 8:48am
Not-a-Fan wrote:
Is he saying the preset factory setting is wrong usually? Seems like the article is cut off :( Seems on one of the pics in the...
Is he saying the preset factory setting is wrong usually? Seems like the article is cut off Sad

Seems on one of the pics in the PV section where is he comparing red spring with different dolly positions, the absolute best most linear delivery setting was screw flush with the case. Seems to me I've been running my pv wrong for years by trusting ktm to set up the motor correctly. Against my instinct to trust the engineers im gonan try my dolly flush next time.


Yea, many come set incorrectly. It seems it happens a lot on the TPi bikes. I have a couple friends with 250’s where the PV was closer to opening after 7k rpm. I normally run mine 1mm to 1.5mm in from flush but set mine closer to flush this week with the yellow spring. Quite a difference in low end.
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Not-a-Fan
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Not-a-Fan 8/2/2022 8:53am
8/2/2022 8:53am Edited Date/Time 8/2/2022 8:57am
Not-a-Fan wrote:
Is he saying the preset factory setting is wrong usually? Seems like the article is cut off :( Seems on one of the pics in the...
Is he saying the preset factory setting is wrong usually? Seems like the article is cut off Sad

Seems on one of the pics in the PV section where is he comparing red spring with different dolly positions, the absolute best most linear delivery setting was screw flush with the case. Seems to me I've been running my pv wrong for years by trusting ktm to set up the motor correctly. Against my instinct to trust the engineers im gonan try my dolly flush next time.


swordfish wrote:
Yea, many come set incorrectly. It seems it happens a lot on the TPi bikes. I have a couple friends with 250’s where the PV was...
Yea, many come set incorrectly. It seems it happens a lot on the TPi bikes. I have a couple friends with 250’s where the PV was closer to opening after 7k rpm. I normally run mine 1mm to 1.5mm in from flush but set mine closer to flush this week with the yellow spring. Quite a difference in low end.
Thanks man. I'm pissed now haha

Just measured my dolly...2.7mm from flush. Wtf lol

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ar15
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ar15 8/2/2022 10:01am
8/2/2022 10:01am
What what should the factory setting for a 2018 KTM SX250 be? The Owners Manual gives a different number than the Repair Manual. See pics.
Owners Manual: 5125 rpm
Repair Manual: 5500 rpm

Quite confusing...



swordfish
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swordfish 8/2/2022 11:09am
8/2/2022 11:09am
ar15 wrote:
What what should the factory setting for a 2018 KTM SX250 be? The Owners Manual gives a different number than the Repair Manual. See pics. Owners...
What what should the factory setting for a 2018 KTM SX250 be? The Owners Manual gives a different number than the Repair Manual. See pics.
Owners Manual: 5125 rpm
Repair Manual: 5500 rpm

Quite confusing...



I’m pretty sure all 250/300’s are supposed to be set at 5500-5600.
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Not-a-Fan
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Not-a-Fan 8/2/2022 11:47am
8/2/2022 11:47am Edited Date/Time 8/2/2022 12:09pm
I'm with swordfish. I would put my money on the 5500/5600 figure depending on which gen motor you have.

Found my owners manual for the previous generation bike and it shows 5600 which matches JDs info above. The 2018 owners manual must have a misprint imo, its gotta be 5500 for you.
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