It is adjusted by releasing the two clamp bolts on the rear of the swinging arm between the sprocket and the disc. Then rotate the castleated Nut with a large C spanner to tightenten or losen the chain. there is a sticker on the swinging arm giving tolerances, check tention with weight on bike befor tightening clamp bolts to 23 foot pounts torque.
I made the C spanner easy to do just cut it out of some 1/4 plate. can gice dimensions if you want. good luck.
Guy Brisbane Australia
Castelated nut is real close up against rear sprocket. The wheel spindle is eccentric to the castelated nut therebye rotating the nut moves the wheel fore and aft and up and down to a degree, so major adjustments change ride height. Guy
You should always turn the eccentric counter clockwise looking at the sprocket side to tighten chain. If in so doing it appears the chain is getting loose keep going as someone adjusted the chain incorrectly at some point. The axle should be in the lower half between 3 and 9 o'clock.