18' KTM 250sx: 60hp motor?

10hp is a pretty significant increase. Relability will become a factor. If it were me id look into hopping up a 450. Theyre probably almost there anyway and with guys like TZR doing crazy shit with KTMs it wouldnt take much to get 60hp.

Mine dynoed almost 51 stock at 22 hours with a rejet, PC pipe and silencer and VP u4.4. Yes it’s possible, but it’s going to take someone that know what’s their doing. Derek at HP Race Development and I talked about it for my bike and he’s pretty confident he can get it there.

AJ565 wrote:

Mine dynoed almost 51 stock at 22 hours with a rejet, PC pipe and silencer and VP u4.4. Yes it’s possible, but it’s going to take someone that know what’s their doing. Derek at HP Race Development and I talked about it for my bike and he’s pretty confident he can get it there.

that's 51at the wheel? not a corrected and bumped up number estimating crank power? everything I saw was suggesting 49-50whp at the crank stock.

already have the exhaust, or did you just pour in race gas and jet it for what I'm guessing is a 8% increase in power over stock with just a exhaust and race gas? or did you have internal work?

or if you had internal work done how much $$ are we talking and what what?

It was done on a chassis dyno. Maybe Derek Harris will see this and chime in about the numbers. The pipe and silencer take it to 49hp per MXA dyno before and after testing from 47hp.

My engine is 100% stock. Only mods are pipe/silencer and jetting. I guess you can count the PV as well, it’s 1 3/4 turns in from all the way out. Switching from C12 to u4.4 was a noticeable difference in power. I’ve posted my jetting in your other threads, but I had to go about 3% bigger on the main and pilot for the oxygen that’s in the fuel. The slide made the biggest improvement in the way the bike runs and I feel is key to getting this engine to wake up.

Put one of these in it. Those bolt in 500cc kits for ktms also look good.

I like the fact there is zero vibration and dont want to need any more lower or midrange power so dont think any of the big bore kits would do anything that im looking for. happy with the bike now but would be happy to spend 1500 or so for 10more hp up top and idk if possible to get it to rev higher.

Yeah the big bores definitely vibrate more! I’m sure u can get the hp out of it. I remember a pc CR250 build in dB mag that was supposed to be 60hp.

10 more HP for just $1,500. In all seriousness, good luck!

Polishhammer wrote:

Yeah the big bores definitely vibrate more! I’m sure u can get the hp out of it. I remember a pc CR250 build in dB mag that was supposed to be 60hp.

It can be done in the hands of the right tuner at getting close to that 60 hp #. The case reed engine can make more power over the traditional cyl. induction fed engine. I've got an 03 CR250r done by PC that is very close in power (butt dyno) to my 18 CRF450r that is estimated at 58 hp atrw..
The low end power is very good with the mid-top / overev that is unmatched to any other 250 2t owned or ridden. I only paid about $300 in 05 which is a very good deal considering the performance of the engine.

OP - I'd suggest contacting PC & consulting with the main guy in the engine dept..

Best bang for the buck in 4 decades of riding mx..

The 03 ktm 250 sx was 55hp so 60 should be possible

Of course it can be done, just look at kart motors. You could get 70HP out of it probably, but wouldn't be very rideable. You're probably better off doing a 300SX and getting the whole engine blue printed. I did that back in 2006 and it was probably 58-60HP, 50/50 C12.

60HP with no loss of bottom or mid? Hahhaaa Good luck. I've ridden quite a few "full mod" 250's done by the big name guys and every one of them sacrificed bottom, mid, and basically all rideability to get big numbers on top.

I raced karts and had multiple 40whp+ 125's that would have been great bike motors that would have been totally rideable, especially the vortex icc motor. 250 motor probably right, the difference in 40whp to 60whp on a mx bike that comes on is probably to dramatic. its not so much the total outright power number that im after its really the way the motor wants to be ridden, something that wants and is rewarding to wring out. I think im in the market for a 350sxf or 250sxf at this point.
I am going to list the bike for sale and see what happens. thanks guys

Might like the 350sxf, broad powerband and revs high. I hear you on the top end. Been riding superbikes for past 10+ years, modified BMW S1000RR's recently so my clapped 2006 YZ250 feels slow so had TMR build it into a 315cc stroker. Obviously totally apples to oranges, but somehow every time I ride dirt I expect to feel more like a superbike. Hard feeling to break.

RCF wrote:

The 03 ktm 250 sx was 55hp so 60 should be possible

Where did you get that HP # from ? In 2003 I seen a dyno graph with 49 hp atrw from the 2003 KTM 250 sx.

https://motocrossactionmag.com/two-stroke-tuesday-2005-ktm-250sx/

FGR01 wrote:

60HP with no loss of bottom or mid? Hahhaaa Good luck. I've ridden quite a few "full mod" 250's done by the big name guys and every one of them sacrificed bottom, mid, and basically all rideability to get big numbers on top.

If you ever make it out to CA. I'd be willing to let you spin a couple of laps on the 03 CR2 with PC engine mods..

A good friend that raced CR500's didn't believe that kind of power could be made from a 250 either. After riding the CR2 he stated that it had comparable HP to his 500's, but was able to go faster on the 250 due to the light weight of the bike & the inertia of the engine allowing for more speed in the corners. After riding the CR2 at some local tracks he sold his 500 to buy a 250.

H4L wrote:

If you ever make it out to CA. I'd be willing to let you spin a couple of laps on the 03 CR2 with PC engine mods..

A good friend that raced CR500's didn't believe that kind of power could be made from a 250 either. After riding the CR2 he stated that it had comparable HP to his 500's, but was able to go faster on the 250 due to the light weight of the bike & the inertia of the engine allowing for more speed in the corners. After riding the CR2 at some local tracks he sold his 500 to buy a 250.

I've ridden a CR250 that essentially had nothing spared by Pro Circuit. It was as I described above.. no bottom end whatsoever and then the top end came on like firing off a missile. Made the powerband feel very disjointed and hard to ride, especially on the rough track I was trying it on. I had a stock CR250 at the time and compared them back to back. Stock was much easier to ride and go fast on. The mod bike may have been faster on a smooth groomed track but was just too unpredictable and hard to make use of on a rough track. The Pro Circuit motor would have been better if they had focused on bottom/mid and made the power broader.

Keep in mind a stock CR500 only has like 55-58 hp, so yeah it's totally possible to get a 250 to those numbers but it won't have near the bottom end of the 500, obviously.

FGR01 wrote:

I've ridden a CR250 that essentially had nothing spared by Pro Circuit. It was as I described above.. no bottom end whatsoever and then the top end came on like firing off a missile. Made the powerband feel very disjointed and hard to ride, especially on the rough track I was trying it on. I had a stock CR250 at the time and compared them back to back. Stock was much easier to ride and go fast on. The mod bike may have been faster on a smooth groomed track but was just too unpredictable and hard to make use of on a rough track. The Pro Circuit motor would have been better if they had focused on bottom/mid and made the power broader.

Keep in mind a stock CR500 only has like 55-58 hp, so yeah it's totally possible to get a 250 to those numbers but it won't have near the bottom end of the 500, obviously.

Not sure how the one you rode was set up, but the 03 CR2 with just cyl. / head mods & no bottom end work runs very strong from a good off idle torque to an exceptional mid-top end / overev.
The 03 has a JD ign. with a Doma exhaust that runs on VP C-12.
If you run their PC pipe combo the powerband will feel as you described with more of a midrange hit that feels like a mule just kicked you.
Yup. The CR500's were making about 55-58 hp atrw..