WHAT IS IT? Dirt Tricks’ automatic KTM cam chain tensioner uses oil pressure, combined with a mechanical ratchet system, to maintain constant pressure on the timing chain (and avoids the possibility of the cam tensioner collapsing during oil pressure fluctuations).
WHAT’S IT COST? $69.95.
WHAT STANDS OUT? Here’s a list of things that stand out with the Dirt Tricks automatic cam chain tensioner.
(1) Oil pressure. The stock KTM cam chain tensioner is hydraulic. It uses pumped oil pressure to press the slider pad against the timing chain. KTM is the only Big Five motocross manufacturer to use hydraulic oil pressure to regulate cam chain slap. Honda, Yamaha, Suzuki and Kawasaki use the traditional spring tension adjuster. Dirt Tricks’ tensioner harnesses KTM’s oil pressure, but mates it with the added benefit of a spring-loaded ratchet system. Best of all, the irritating ticking sound that KTMs make on warm-up is reduced because the engine doesn’t have to wait for the oil pressure to build up before the timing chain is buffered.
(2) Ratchet. Why is the ratchet system so cool? The OEM components have a serious flaw in that fluctuations in engine oil pressure can allow the cam chain tensioner to back off from the slider pad (leaving the cam chain loose). Dirt Tricks’ cam chain tensioner still uses oil pressure, but backs it up with a spring-and-ratchet system, which prevents the slider pad from backing off. There are 11 ratchet clicks on the Dirt Tricks unit.
(3) Fitment. The Dirt Tricks cam chain tensioner works on 2005 to 2009 KTM 250 four-strokes, 2007 to 2009 450SXFs, 2008 and 2009 400, 450, 505, 530 XC and EXC models and all models that use RC4, XC4 or RF4 engines (including Husabergs). It does not work on the RFS engine.
(4) Installation. It takes about five minutes to install the Dirt Tricks cam chain tensioner. It uses the stock KTM caps and seals so that the oil pressure system is not compromised.
WHAT’S THE SQUAWK? We don’t have one. It should be noted that the KTM race team uses a ratcheting cam chain tensioner. This is simple, textbook engineering.
It is easy to overlook the value of a cam chain tensioner, but the next time you start your KTM four-stroke and hear that awful clatter, you’ll know the importance of a properly adjusted cam chain tensioner.
KTM Motorcycle tests