2017 ktm 150sx motor mods

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2/2/2018 4:04 PM

Have a 17 ktm 150sx has full hgs exhaust , v-force 4 , 13/46 gearing and jetted for vp u4.4 race fuel bikes crisp . Looking to do full mod motor but looking to get head done first get the squish correct , my dads 17 ktm 150xcw had head done compression ratio is 17.5:1 is this too high or about right for this motor . Any help would be appreciated Photo

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2/2/2018 4:45 PM

Don't forget you can easily tighten up the squish gap with the optional thickness gaskets.

Fmf pipe did better than hgs on the dyno

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2/2/2018 5:01 PM

Bruce372 wrote:

Don't forget you can easily tighten up the squish gap with the optional thickness gaskets.

Fmf pipe did better than hgs on the dyno

Thanks for the info Bruce I'll try that route with thinner gasket and that's no good ended up selling exhaust to my buddy lol down the road may just get another fmf if hgs doesn't work very well .

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2/2/2018 6:55 PM

have a 18sx150 bills pipe on it lectron carb 49 rear sprocket v force runs great

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[Moto D Racing

2/2/2018 9:44 PM

werner822 wrote:

Have a 17 ktm 150sx has full hgs exhaust , v-force 4 , 13/46 gearing and jetted for vp u4.4 race fuel bikes crisp . Looking to do full mod motor but looking to get head done first get the squish correct , my dads 17 ktm 150xcw had head done compression ratio is 17.5:1 is this too high or about right for this motor . Any help would be appreciated Photo

Have a 150SX with Doma/SXS Pipe and Vforce4

I dont know what you ride but a 13/46 gearing is a
bit to much for MX Track
I ride 13/50

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2/2/2018 9:51 PM

How is the Performance of the HGS Pipe , think about to buy one.
About the Motortuning, i spoke with a German Engine Tuner in Dezember.
And he told me the 2016+ Models are so good from the Factory that you can only make 5% more Power
with a full Engine Modification.

On the 2011-2015 Bikes he can make 13-15% more Power.
So i save the Money and spend in good Suspension Service.

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2/3/2018 6:33 AM

Bruce372 wrote:

Don't forget you can easily tighten up the squish gap with the optional thickness gaskets.

Fmf pipe did better than hgs on the dyno

werner822 wrote:

Thanks for the info Bruce I'll try that route with thinner gasket and that's no good ended up selling exhaust to my buddy lol down the road may just get another fmf if hgs doesn't work very well .

What mm gasket should I go with they have .75mm all the way down to .20mm I run straight race fuel vp u4.4 . Thank you

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2/3/2018 6:36 AM

KTM Two Stroke wrote:

How is the Performance of the HGS Pipe , think about to buy one.
About the Motortuning, i spoke with a German Engine Tuner in Dezember.
And he told me the 2016+ Models are so good from the Factory that you can only make 5% more Power
with a full Engine Modification.

On the 2011-2015 Bikes he can make 13-15% more Power.
So i save the Money and spend in good Suspension Service.

I like the hgs a lot only rode it one time indoors and the gearing combo was way too tall for indoor but the bike seems to rip with it , they say the best mod you can do is to run race gas and increase the compression to get the squish right which fixes a lot of jetting issues also . My dad has a full Doma setup on his 17 ktm 150xcw and he loves it

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2/3/2018 6:38 AM

honda70 wrote:

have a 18sx150 bills pipe on it lectron carb 49 rear sprocket v force runs great

Those bills setup look amazing , I got the jetting dialed on it but definitely is more finicky then your caberuator

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2/3/2018 12:00 PM

Bruce372 wrote:

Don't forget you can easily tighten up the squish gap with the optional thickness gaskets.

Fmf pipe did better than hgs on the dyno

werner822 wrote:

Thanks for the info Bruce I'll try that route with thinner gasket and that's no good ended up selling exhaust to my buddy lol down the road may just get another fmf if hgs doesn't work very well .

werner822 wrote:

What mm gasket should I go with they have .75mm all the way down to .20mm I run straight race fuel vp u4.4 . Thank you

I've been trying to find out stock gasket thickness but no one knows.

I've had bills and doma pipes on my old rm125 and they are great pipes. The hgs sounds like a top end screamer, probably gives up a little mid range to the fmf

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2/4/2018 7:26 AM

The proper base gasket thickness used is supposed to give you the proper " X " dimension . "X" dimension is the distance from the top of the piston ( at top dead center ) to the top of the cylinder . This "X" dimension is listed in a chart in your Ktm owner manual in the back section with other specs























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2/5/2018 8:24 AM

2stmark wrote:

The proper base gasket thickness used is supposed to give you the proper " X " dimension . "X" dimension is the distance from the top of the piston ( at top dead center ) to the top of the cylinder . This "X" dimension is listed in a chart in your Ktm owner manual in the back section with other specs























Thanks 2stmark for the reply , I think I am just going to send the cylinder and head out in the next 5 hours when I do a new piston and then I don't have to mess at all with getting the squish correct they can worry about it lol .

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6/7/2019 5:53 AM

I have an 150sx 2018. B class
Sproket 13/46
Power valve unscrewed at max.
37.5 pilot 540 main
Ride mainly in a sandy track and the bike ride awsome.
If you didnt try the 13 46 gearing. Try it before commenting badly about it. With the stock gearing i was cornering in 3rd and the 4th gear miss just a little to work too , lol goin with 13 49 or 50 you should cornering in 4 and get the 6 all out in the strech for sure.

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6/7/2019 6:28 AM

All the 150sx's I worked on had two base gaskets stacked together: 0.40mm + 0.25mm = 0.65mm total base gasket thickness. This set the "X" dimension at -0.0025" or 0.064mm where the piston was sub-flush from the cylinder deck. I tried like heck to get more out of the motor by raising or lowering the cylinder and it lost power or just moved it around. The best mod for me was an OEM Keihin Air stryker and carb flange from the '16 150. Motorex 2T premix at 40:1 and 50:50 C12/91 pump with an FMF factory fatty and shorty combo. This made 42.2hp on a known Dynojet dyno. it was the best two stroke I've ever ridden. I also tried tightening the squish with little to no gain. KTM did a good job optimizing the engine and finding huge gains was tough. I also had the stock powervalve spring set at 0.10mm in from flush (flush = all the way out)

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6/7/2019 6:50 AM

werner822 wrote:

Have a 17 ktm 150sx has full hgs exhaust , v-force 4 , 13/46 gearing and jetted for vp u4.4 race fuel bikes crisp . Looking to do full mod motor but looking to get head done first get the squish correct , my dads 17 ktm 150xcw had head done compression ratio is 17.5:1 is this too high or about right for this motor . Any help would be appreciated Photo

What's he running for fuel at 17:1 compression, low sulphur diesel? That's a massively high compression ratio for any gasoline engine, 4 strokes up to maybe 13:1 at the higher side of things, that's butt nutty at 17:1.

But as for mods, I milled 1mm off of my 16 125 head surfaces and then set my piston height to 1mm below the top of the cylinder. This raises all port heights, which for a 150, is a good thing, as the cylinder castings between the 125 and the 150, are the same, but the bigger bore of the 58mm piston affects port heights by lowering them due to the larger bore removing more of the port area, lowering all port heights in comparison to a standard 125 bore. This little mod was cheap, and worked wonders in my 125, so I can imagine it would be even more benificial to do this to a 150, due to the displacement increase. Next up, steel clutch plates, there are 2 steel and 4 aluminum clutch drive discs, remove the 4 alu plates and swap them for steels, this will help the Clutch pack from slipping, my 125 at wide open, was slipping clutch, and simpley adding all steel clutch plates added a lot of top end speed, and I could feel the bike was way faster down the straits afterwards, plus steel clutch plates extend oil life by not contaminating it as quickly as alu plates will, as for exhausts, I had the fmf, and it wasn't really much better than stock, other than it helped to fill the the dip in the power curve, but I did feel my pro circuit works pipe and r304 woke the engine up waaaay better than the fmf did, but, I sold my 16 125 due to it being tooooo light for a 6' 180lb rider, had the suspension set up for my weight, and the bike was no slouch as Iv mainly owned smallbore 2 strokes most of my life, and can ride them like intended. These are no slouches when it comes to laying down some pow, but they need massaging, and to be honest your best interest, is to get rid of the stock Reed block as it's so flawed from the factory, like a purely bad design, I did try the v4 block in this, and felt it sealed up better but the reed stopped robbed a ton of top end power, and my modified stock block out flowed it up too easily, I never got the chance to run the radvalve, as I sold the bike before it was released to my disappointment, but Iv always gotten better results with rad valves over the vforce blocks, and Iv tried vforce on lots of the bikes Iv owned thru the years, yz125/250, both better with radvalve over vforce, cr250, radvalve blew the vforce
Out of the water easily, and on my 2012 250sx, the radvalve was hands down superior to the vforce. But if you were to choose I'd almost go with the 250sx radvalve over the 125, as the 150 could probably make use of the 250's extra room in the Reed block for better flow up top, same base plates between the two, as they come with the same Reed block from the factory for all ktm 2 strokes now (pretty lame :/ ).


Anyone looking for a 125/150 pro circuit exhaust??!?!!? Iv got one up fer salé, next to new condition

Pm if interested, give me your addy, and I'll get a quote on shipping and we can hammer out a price.

Photo
Photo

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6/7/2019 6:54 AM
Edited Date/Time: 6/7/2019 7:45 AM

DynoDan22 wrote:

All the 150sx's I worked on had two base gaskets stacked together: 0.40mm + 0.25mm = 0.65mm total base gasket thickness. This set the "X" dimension at -0.0025" or 0.064mm where the piston was sub-flush from the cylinder deck. I tried like heck to get more out of the motor by raising or lowering the cylinder and it lost power or just moved it around. The best mod for me was an OEM Keihin Air stryker and carb flange from the '16 150. Motorex 2T premix at 40:1 and 50:50 C12/91 pump with an FMF factory fatty and shorty combo. This made 42.2hp on a known Dynojet dyno. it was the best two stroke I've ever ridden. I also tried tightening the squish with little to no gain. KTM did a good job optimizing the engine and finding huge gains was tough. I also had the stock powervalve spring set at 0.10mm in from flush (flush = all the way out)

Another nice mod that might pay dividends in power delivery, is the optional 1.8mm primary spring that comes in the 150xc, I tried it in my 125 with a pwk36s, and it wasn't overly happy with it, but I'm willing to bet the bigger piston vs the 125's crank case volume, would probably work wonders and make a lot more bottom, and fatter mid, with a smoother transition into the top end, and even mxa said they could run slacker power valve settings with the 150 over the 125 and get more bottom and mid, and that will make for less of a transition into the top end, resulting in a smoother powerband. Also....... I have measured gudgeon pin heights on the ktm 125/144/150 pistons.... and they are all 22mm. And the mainbearings, drive gear, and flywheel stub are all the same, Iv cross referenced all the part numbers surrounding the ktm smallbore bottom ends, and the part numbers match out between the old 125/144 engine, and the new 125/150.
Crankshafts are dimensionally identical, as vhm states one part number for each other cranks, middle/high inertia, hot rods, the same, wiseco same, all of the 125/150 cranks are the same for 1999-2019.

So I'll get to my point, if all ktm did for the new crank is shave 2oz Off it, and if the piston gudgeon pin heights are the same between the 54/56/58mm pistons, then technically, (I don't know this for sure, but Iv done enough reading on this subject) but if the cylinder heights between the new 125 and 150 are the same, it should be possible to take an old generation 144/150 58m crankshaft, and litterally drop it into your existing cases with zero modifications, like direct bolt in, using oem parts if you so wish, with zero grinding involved, a literal bolt in stroker crank for the new 150's.... turning it into a 154cc engine.

Sorry for this, but you opened up Pandora's box with this topic, as I'm a severe fan of ktm smallbores, love them to death.

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6/7/2019 7:05 AM

Ps, vhm did dyno testing, and made 46whp with a hgs exhaust, and a vhm head and proper tuning

https://m.

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6/7/2019 9:08 PM

2stmark wrote:

The proper base gasket thickness used is supposed to give you the proper " X " dimension . "X" dimension is the distance from the top of the piston ( at top dead center ) to the top of the cylinder . This "X" dimension is listed in a chart in your Ktm owner manual in the back section with other specs























werner822 wrote:

Thanks 2stmark for the reply , I think I am just going to send the cylinder and head out in the next 5 hours when I do a new piston and then I don't have to mess at all with getting the squish correct they can worry about it lol .

you have to measure the squish clearance you currently have if you want them to set it. unless you are sending the whole motor.

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6/11/2019 10:28 AM

VHM head, Doma exhaust and some port work. That’s what I did to my 16 when I had it and was an awesome bike. When fresh, it would rival 250f’s, but after sort of 30/40 hours I found they start to lose a lot of power if they’ve been rode hard.

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6/11/2019 10:33 AM

I just threw a 38mm PWK Air Stryker on our 17 TC125 and it was a night and day difference. I'm sure you can get the Mikuni to work but I have a box of Keihin jets and the PWK is much more set and forget. .........I am waiting to go through rest of setup until first rebuild. Had fresh top end when we picked it up........

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6/18/2019 9:31 PM
Edited Date/Time: 6/18/2019 9:32 PM

Slavens HV Lectron carb on my 2019 150sx. Incredible. I'll leave it at that.

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6/19/2019 8:19 PM

werner822 wrote:

Have a 17 ktm 150sx has full hgs exhaust , v-force 4 , 13/46 gearing and jetted for vp u4.4 race fuel bikes crisp . Looking to do full mod motor but looking to get head done first get the squish correct , my dads 17 ktm 150xcw had head done compression ratio is 17.5:1 is this too high or about right for this motor . Any help would be appreciated Photo

KTM Two Stroke wrote:

Have a 150SX with Doma/SXS Pipe and Vforce4

I dont know what you ride but a 13/46 gearing is a
bit to much for MX Track
I ride 13/50

I ride/race my 16 150sx in the woods & moto ….13/52 !
I use 6th

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