Also offered is the 250XC-w which is said to have a wider ratio transmission and be the most mellow version of the three. While these bikes differ in more ways than one, the head is an area where KTM can easily change the characteristics of one bike compared to the other. Altering the compression of an engine can do a lot to the power of an engine. The SX has higher compression than the XC, and the XC higher than the XC-w. Higher compression generally makes more power, but can also make an engine less reliable and/or less rideable if not done properly or kept in check. Elevation gain actually lowers compression, so the compression an engine makes will tend to be more of an issue for those that ride at higher elevations. Having these heads that are interchangeable factory options made a nice easy and safe way to give my 2010 KTM 250XC a power boost. I picked the head up for $164, add new o-rings for under ten bucks and some shipping and I was ready to go. The part numbers are almost identical, but do vary with one number. The 250 xc # is 54830106300, 250 sx # 54830106400, and the 250 xc-w # is 54830106200. This really is an easy swap, just unbolt the old head and re-bolt and re-torque the new head. Be sure to get new o-rings any time you remove the head.
|Here you can see the difference in the heads. XC head on the left, SX on the right.|
The shallow bowl of the SX head makes more compression.
|Top view. The SX head on the right has a deeper hole for the plug because of the shallow bowl.|
The casting is identical, just differences in machining.