The 2008 and newer four-stroke KTMs (and some earlier SX models) use a timing chain tensioning device intended to develop its force using the engine oil pressure hydraulically. The OEM components have serious flaws (reviewed below), which can leave the timing chain in a slack condition. This can have disastrous consequences.  Dirt Tricks has developed a simple, effective, and failsafe replacement. The new tensioner correctly captures the oil pressure. Additionally, it uses a positive mechanical ratcheting system which prevents it from collapsing. The replacement unit will work on all newer four-strokes in 250, 400, 450, 505, and 530 models using the RC4, XC4, or RF4 motor (not for the RFS motors). This means the following bikes:

• 2005-2011  all 250 four-stroke models.

• 2007-2011  450 SX-F and 450 SXS-F models.

• 2008-2011  all 400, 450, 505, 530 four-stroke models.

With very satisfying test results from our race bikes, we have completed CNC production of the new tensioner. They can be installed in less than five minutes.

As the spring is inserted and you compress it, you can feel and hear the clicks as the piston ratchets into position. There are a total of 11 ratchet positions at 1mm spacing. If you extend to more than 9 clicks, you probably need to replace your timing chain.