After plunking around here and on KTMtalk, I decided to look further into a head mod for my 2006 KTM 250 XC-W. Got some ideas about doing headwork on the existing head, then other ideas stating that the XC-W head was not such a great head to mod and to get the 250 SX head instead. So when I was shopping around on eBay, I found this and bought it:

SXS Cylinder Head Kit 250 SX
Cylinder Head with 3 exchangeable combustion chamber inserts, so you can adjust the power delivery for different track conditions.



So I am thinking one of these inserts "should" give me the low end grunt I feel I am lacking on my 250. Does anyone have any experience or knowledge of this particular kit? I may well be the first to try it out, but figure maybe someone has tried it before.

Take it fwiw, but I had the 05 250EXC (same bike as yours) and no amount of little mods would wake the lowend up. I ended up doing what everybody else ended up doing back then and that was specing the engine to the SX (head, piston) and aftermarket pipe. Out of curiosity, where is the deck height set at?

I got the bike used so not sure where the deck height is set...is that determined by base gasket below the cylinder or am I thinking of something else? I have not done any top end work on it---I have only had for a couple of months now. I was thinking the EXC probably had more low end than my XCW, so that is surprising to hear.

Regarding that kit...I can't tell if the kit comes with a standard SX250 head along with the inserts, or if it is a specially designed SX head that accomodates the inserts. I don't know anyone with an SX250 to compare.

the 05 EXC and XCW were basically the same machine...but the 06 did run a bit better down low than the 05. The 05 was one of the softest running 250 engines KTM has ever built, i mean downright anemic down low.

I always set my deck height at flush. When you have the head off, with the piston at TDC you can measure it. You can also change that measurement with the different base gasket thicknesses available. All that aside, the SX piston and head sure woke the bike up. I am not familiar with the head inserts with regards to how it performs with the existing piston. I guess give it a try after checking the deck height and report back. The SX spec'd 05 engine had an instant bark with pull all the way through, no dead spots at the low to mid transition. No soft throttle response, just bark. Nothing as strong as say my 11' SX250, but no other 250 2T is either.

Do you really want to go thru o rings and coolant draining on a regular basis?? IMHO, I would pick up an SX head, go up 2 teeth in the rear, pick up a used SX CDI, and ride it. Then determine if you need more, but I doubt you will.

gmoss, on 04 February 2012 - 09:23 PM, said:

No, I do not really want to fool with it a lot---the kit idea looked interesting at the time when I bought it since I did not want to be stuck with only one upgrade option... but now maybe not so interesting when you put it that way. Maybe I will get "lucky" and dial it in okay enough with one of the inserts.

ktmwade, on 04 February 2012 - 01:09 PM, said:

Hmm, had not seen a whole lot of discussion about changing the piston, mostly the head. I guess I may be back to the drawing board soon. But I am holding out some hope that one of the inserts will be satisfactory. Figuring that the bigger the insert the better the compression?? But maybe not so simple as that.

Iirc, the 06 went to the same piston across the board for the XCW/XC and SX but I cant remember for sure. The prior years used a different piston for the EXC heads

On the SXS kit I went with the supercross insert (the 19cc one) and never bothered with the other inserts. Run it with a 2006+ domed piston and enjoy the the torque. It runs fine on 89+ pump gas and with an X dimension of -.04mm (piston slightly above the cylinder deck) I had a squish clearance of .058". For a short time I ran it with no base gasket and race gas but it changed the port timing enough to kill the top end power. It runs great and has a ton of off idle torque. I run a later model 250SX ignition as well and can bog it down as low as 4 stroke with very little stalling.

I got mine on ebay as well (new closeout) , the $250 retail price is a bit much.

gmoss, on 04 February 2012 - 09:23 PM, said:

Why do you think it would require frequent o-ring changes? I had similar heads on different jet skis, some pushing 220PSI cranking pressure & o-rings lasted a year of riding every weekend, including some sustained WFO running to top speed for minutes at a time (riding a lake or river when the waves were flat).

if you are swapping head inserts for different races, trails etc, then you will be going thru O rings. If you pick one and stick with it, why do you need the other inserts. To me, having the head milled is a better alternative....

Having different domes to insert in a head allows you to switch to high compression and run race fuel for races then switch to lower compression and pump gas for practice. For the casual rider looking to get more grunt, spec out the engine and have a head modified.
Joe.........