KTM SX 150....searching for more over rev.

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12/28/2018 9:00 PM

Hey guy's , one of my best bud's ( Wardy ) is getting ready to tear down his 14' KTM SX150. He asked me if I knew of a way to get a tad bit more over rev out of it , without sacrificing to much bottom and mid. His motor is bone stock , except for a bill's pipe and silencer. For a 150 , she has good grunt through the bottom and mid , and he's looking to add a little over-rev. Any suggestion's?

I know some guy's have played around with base gasket height , milling the head and so forth. I told him to call Boyesen and ask about a different set of reed pedal's ( stiffer or softer than stock? ) Obviously porting , or carb mods something similar may help? Just wondering where it might be a good place to start?

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

12/28/2018 11:49 PM

125 barrel and piston?

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12/29/2018 2:31 AM

Aftermarket ignition to drive an electronic powerjet carb so it leans at the right spot in overrev and it’ll rev on further.

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12/29/2018 8:01 AM

Which silencer? A longer one helps out on the top end. If he's open to it try a different brand of exhaust.

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2018 KTM 250sx
Instagram CamaroAJ

12/29/2018 9:52 AM

I believe he's running the longer silencer. He did mention something about possibly changing the ignition as well. I'm not sure exactly how much he plans on putting into this bike with it being a '14 , but he's pretty happy with the bike overall , just wanted some idea's on how to improve the over-rev a bit.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

12/29/2018 11:49 AM

HGS pipe cave my 150sx alot more over rev than the stock pipe and after adding BUD racing cylinder head it revved even further.

I heard that some guys are running 125 SXS ignition control units in their 150's in search of more over rev but I think it might make 150sx tendency to detonate even worse https://www.ktm-parts.com/SXS15125390.html

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12/30/2018 6:09 AM

I heard the SXS ignition helps. Get a port job from Millenium Technology and have them focus on over rev.

Has he adjusted his power valve setting?

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12/30/2018 5:08 PM

lift the upper exhaust port edge

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12/30/2018 6:14 PM

WEAL wrote:

lift the upper exhaust port edge

Doesn’t want to lose bottom mid.

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12/30/2018 10:35 PM

Heard good things about STIC carb mod letting the by rip on top

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12/31/2018 7:25 AM

I have a 14 KTM 150 SX. An FMF pipe and shorty silencer made the power more broad, particularly with more over rev and not falling off as hard.

Putting a thinner base gasket with stock head improved low end and pull into midrange as well, with minimal change in top end and over rev. With stock gasket setup, lower RPM range isn't quite as clean running but does rev out slightly better. The thinner base gasket makes it easier to ride.

Recently, I added a STIC metering block to the carburetor. Definitely added more top end and over rev. Low end feels similar to stock and mid range is stronger but jetting is not optimized yet.

I also have tested the SXS 125 ignition. Feels like a very racy 125 with that setup, but wasn't the feel I was looking for. Will sell the ignition for $75 shipped if your buddy is interested.

On gearing, the stock 48 tooth gives it the broadest spread of gearing. Have tried 48, 49, 50, and 51. All the larger sprockets meant was more shifting and less drive as it revs through RPM range too fast.

And a safety note: I roasted my stock cylinder when the stupid check valve ball in the gas cap stuck causing an extreme (but intermittent) lean condition. Would highly recommend taking that POS out.

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12/31/2018 10:37 PM

erik_94COBRA wrote:

I have a 14 KTM 150 SX. An FMF pipe and shorty silencer made the power more broad, particularly with more over rev and not falling off as hard.

Putting a thinner base gasket with stock head improved low end and pull into midrange as well, with minimal change in top end and over rev. With stock gasket setup, lower RPM range isn't quite as clean running but does rev out slightly better. The thinner base gasket makes it easier to ride.

Recently, I added a STIC metering block to the carburetor. Definitely added more top end and over rev. Low end feels similar to stock and mid range is stronger but jetting is not optimized yet.

I also have tested the SXS 125 ignition. Feels like a very racy 125 with that setup, but wasn't the feel I was looking for. Will sell the ignition for $75 shipped if your buddy is interested.

On gearing, the stock 48 tooth gives it the broadest spread of gearing. Have tried 48, 49, 50, and 51. All the larger sprockets meant was more shifting and less drive as it revs through RPM range too fast.

And a safety note: I roasted my stock cylinder when the stupid check valve ball in the gas cap stuck causing an extreme (but intermittent) lean condition. Would highly recommend taking that POS out.

Thanks Erik! My buddy actually just saw your post here and he is really interested in that SXS Ignition. Can you send me a PM with a way for either him or me to get in contact with you? I can give you my word , he's about as a strait shooter as you can get. Been one of my best friends and riding buddies going on about 25 years.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/1/2019 9:51 AM

I too wish my 18 150SX had more top end over rev. I got a Keihin carb, FMF 2.1 shorty, Vforce, FMF fatty. I'm overall happy where it's at, just would like to rev out a little further. May go for the STIC next or possibly a port job by Lynks. I hear they are the go to guys for the KTM small bore 2-strokes.

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1/1/2019 10:38 AM

macz400 wrote:

I too wish my 18 150SX had more top end over rev. I got a Keihin carb, FMF 2.1 shorty, Vforce, FMF fatty. I'm overall happy where it's at, just would like to rev out a little further. May go for the STIC next or possibly a port job by Lynks. I hear they are the go to guys for the KTM small bore 2-strokes.

If you send your Cylinder to Lynks Racing please give a Feedback about the Performance.
Read the Article from the MXA 150SX Four Stroke Fighter with the Lynks Racing Tuning

Have a 2016 150 with Doma Pipe /VForce4 and
Cone Valve Fork.
Think about switch to FMF Exhaust
Which Setup do you run in your Keihin Carburator?

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1/1/2019 2:02 PM

STIC metering block.

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1/1/2019 3:36 PM

People doing the pwk swap maybe should do the PWM carb as it’s more top end orientated. I read a Kart tuner say that the Air Stryker carb costs top end because the foils at WOT disrupt the airflow.

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1/1/2019 3:38 PM

Jrewing wrote:

People doing the pwk swap maybe should do the PWM carb as it’s more top end orientated. I read a Kart tuner say that the Air Stryker carb costs top end because the foils at WOT disrupt the airflow.

who uses PWM carbs any longer on bikes? A kart's top end needs are a lot different than a dirt bike fwiw.

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vomiting equals disqualification.

1/1/2019 3:45 PM

Jrewing wrote:

People doing the pwk swap maybe should do the PWM carb as it’s more top end orientated. I read a Kart tuner say that the Air Stryker carb costs top end because the foils at WOT disrupt the airflow.

BR8ES wrote:

who uses PWM carbs any longer on bikes? A kart's top end needs are a lot different than a dirt bike fwiw.

They probably aren’t popular because of the PJ style choke idle setup.

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1/1/2019 3:50 PM

Jrewing wrote:

People doing the pwk swap maybe should do the PWM carb as it’s more top end orientated. I read a Kart tuner say that the Air Stryker carb costs top end because the foils at WOT disrupt the airflow.

BR8ES wrote:

who uses PWM carbs any longer on bikes? A kart's top end needs are a lot different than a dirt bike fwiw.

Jrewing wrote:

They probably aren’t popular because of the PJ style choke idle setup.

GET ignition have a setup for those. An Aussie tuner does a head and mapped GET that dynos pretty good.

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1/1/2019 3:55 PM

I still think a proper setup head, modified powerjet carb and a mapped cdi to switch it as the bike falls off the pipe would be the best setup.

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1/1/2019 3:58 PM

BR8ES wrote:

who uses PWM carbs any longer on bikes? A kart's top end needs are a lot different than a dirt bike fwiw.

Jrewing wrote:

They probably aren’t popular because of the PJ style choke idle setup.

Jrewing wrote:

GET ignition have a setup for those. An Aussie tuner does a head and mapped GET that dynos pretty good.

I did see the GET set up... interesting. I have the Vortex and like it.

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vomiting equals disqualification.

1/1/2019 5:39 PM

macz400 wrote:

I too wish my 18 150SX had more top end over rev. I got a Keihin carb, FMF 2.1 shorty, Vforce, FMF fatty. I'm overall happy where it's at, just would like to rev out a little further. May go for the STIC next or possibly a port job by Lynks. I hear they are the go to guys for the KTM small bore 2-strokes.

Remove the shorty and go back to stock. You ought to gain a bit of top end

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1/1/2019 6:38 PM

erik_94COBRA wrote:

I have a 14 KTM 150 SX. An FMF pipe and shorty silencer made the power more broad, particularly with more over rev and not falling off as hard.

Putting a thinner base gasket with stock head improved low end and pull into midrange as well, with minimal change in top end and over rev. With stock gasket setup, lower RPM range isn't quite as clean running but does rev out slightly better. The thinner base gasket makes it easier to ride.

Recently, I added a STIC metering block to the carburetor. Definitely added more top end and over rev. Low end feels similar to stock and mid range is stronger but jetting is not optimized yet.

I also have tested the SXS 125 ignition. Feels like a very racy 125 with that setup, but wasn't the feel I was looking for. Will sell the ignition for $75 shipped if your buddy is interested.

On gearing, the stock 48 tooth gives it the broadest spread of gearing. Have tried 48, 49, 50, and 51. All the larger sprockets meant was more shifting and less drive as it revs through RPM range too fast.

And a safety note: I roasted my stock cylinder when the stupid check valve ball in the gas cap stuck causing an extreme (but intermittent) lean condition. Would highly recommend taking that POS out.

jeffro503 wrote:

Thanks Erik! My buddy actually just saw your post here and he is really interested in that SXS Ignition. Can you send me a PM with a way for either him or me to get in contact with you? I can give you my word , he's about as a strait shooter as you can get. Been one of my best friends and riding buddies going on about 25 years.

Sent you a PM. I hate this system so if it doesn't come through LMK.

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1/1/2019 8:19 PM

macz400 wrote:

I too wish my 18 150SX had more top end over rev. I got a Keihin carb, FMF 2.1 shorty, Vforce, FMF fatty. I'm overall happy where it's at, just would like to rev out a little further. May go for the STIC next or possibly a port job by Lynks. I hear they are the go to guys for the KTM small bore 2-strokes.

colintrax wrote:

Remove the shorty and go back to stock. You ought to gain a bit of top end

I have the stock silencer, FMF shorty, and FMF 2.1 . Believe it or not the shorty felt like it let the bike rev a little further than the stock one. Also had way better throttle response and power than both the other silencers.

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1/1/2019 9:29 PM

erik_94COBRA wrote:

I have a 14 KTM 150 SX. An FMF pipe and shorty silencer made the power more broad, particularly with more over rev and not falling off as hard.

Putting a thinner base gasket with stock head improved low end and pull into midrange as well, with minimal change in top end and over rev. With stock gasket setup, lower RPM range isn't quite as clean running but does rev out slightly better. The thinner base gasket makes it easier to ride.

Recently, I added a STIC metering block to the carburetor. Definitely added more top end and over rev. Low end feels similar to stock and mid range is stronger but jetting is not optimized yet.

I also have tested the SXS 125 ignition. Feels like a very racy 125 with that setup, but wasn't the feel I was looking for. Will sell the ignition for $75 shipped if your buddy is interested.

On gearing, the stock 48 tooth gives it the broadest spread of gearing. Have tried 48, 49, 50, and 51. All the larger sprockets meant was more shifting and less drive as it revs through RPM range too fast.

And a safety note: I roasted my stock cylinder when the stupid check valve ball in the gas cap stuck causing an extreme (but intermittent) lean condition. Would highly recommend taking that POS out.

jeffro503 wrote:

Thanks Erik! My buddy actually just saw your post here and he is really interested in that SXS Ignition. Can you send me a PM with a way for either him or me to get in contact with you? I can give you my word , he's about as a strait shooter as you can get. Been one of my best friends and riding buddies going on about 25 years.

erik_94COBRA wrote:

Sent you a PM. I hate this system so if it doesn't come through LMK.

I didn't get one Erik. I'll try sending you one. If you don't get that one , we'll think of a way. You got my buddy all worked up on this thing now haha. I'm curious as well whet this ignition may be like.

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And there goes Jeffro. One of God's own prototypes. A super high-powered mutant of some kind never even considered for mass production. Too weird to live, and too rare to die.

Pimpin' Ho's , Rollin' fatty's......drinkin' beers , beers , beers!! ~ Ja

1/1/2019 11:17 PM

macz400 wrote:

I too wish my 18 150SX had more top end over rev. I got a Keihin carb, FMF 2.1 shorty, Vforce, FMF fatty. I'm overall happy where it's at, just would like to rev out a little further. May go for the STIC next or possibly a port job by Lynks. I hear they are the go to guys for the KTM small bore 2-strokes.

colintrax wrote:

Remove the shorty and go back to stock. You ought to gain a bit of top end

macz400 wrote:

I have the stock silencer, FMF shorty, and FMF 2.1 . Believe it or not the shorty felt like it let the bike rev a little further than the stock one. Also had way better throttle response and power than both the other silencers.

I have tried a bunch of silencers(Stock, Shorty, Bud Racing Carbon Fiber, PowerCore and Turbinecore). Here’s my thoughts, initial thoughts, just 2 cents.

Stock- Baseline power

Shorty- More bottom end, less over rev then stock

Bud Racing- Simaler to stock/Could argue a little less or little more power. It was bought used so maybe new packing could help

PowerCore-Simaler to stock/Could argue a little less or little more power. It was bought used so maybe new packing could help

Turbinecore- has Spark arrestor. Less bottom end, power feels less but smoother overall then stock, call me crazy but I feel like it revs farther.

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1/2/2019 2:42 PM

A guy on here dynoed a 2018 tc125 and found (against convention) that the fmf shorty made the best over rev.

Problem here is that the bike needs to go on a dyno to test all this stuff out properly.

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