This is a billett aluminum tensioner made by Shockwave. It mounts to the bearing cassette and the plastic bolt presses against the mount to keep your motor in place. It is adjustable so that you are able to change the slack on your chain when changing sprockets, etc. If your kart did not come with one than it is highly recommended. It stops your motor from sliding on the frame rails which can cause a thrown chain.
Mounting Holes Center to Center: Approx. 90mm apart (works on CRG)
Comes with or without the Stop Bolt