That is a second gen VM and is wrong for the bike. I have replaced it with a first gen. On this version, the triangle on top of the tension arm twists and make the flappers on the chain stay move to change gears.

The first gen is a simple lever chain tensioner. Push it forward, the chain loosens. Grab the chain with your hand to change gears. Push the lever back to retension the chain. As easy as 1-2-3.