After a short ride (~15 minutes) and with the bike on the side stand, place your tape measure next to the chain with the tape extended enough so that it goes past the chain about 2 inches, in about the center of it (between the two sprockets).
To measure - note where the middle of the chain link is on the tape measure. Push the chain upwards and note where the center of the link is. It should be between .8" and 1.2".
To adjust - Using the pliers, remove the cotter pin on the left side of the rear wheel's axle. Then with the 22mm (left side) wrench and 17mm (right side) wrench loosen the rear axle nut by rotating counterclockwise on the 22mm nut. Be sure to loosen the 22mm nut, not the 17mm axle bolt. There is no need to remove the nut, but loosen it in order to allow the wheel to move as necessary. Using the 12mm wrench, adjust the screws and plates on the back of the swing arm by turning the nuts attached to each. Be sure to do each side equally and in small increments. There are markings on the swing arm noted near the axle. Make sure they line up while you are adjusting the chain tension.
To tighten the chain - turn the nuts clockwise. The plates may become loose. You might need to pull the wheel backwards or roll the bike in order to get the plates to be flush with the swing arm again.
To loosen the chain - turn the nuts counterclockwise. This allows the wheel to be pushed forward allowing the chain tension to loosen up. The plates will become loose. Block the rear wheel, grab the grab-rail and pull; this will move the wheel forward.
Be sure to adjust the nuts on the left and right sides equally and at roughly the same time. Doing so allows the chain to tension properly and not cause the wheel to be off center.
It is suggested to tighten in small amounts at a time, as it is easier to tighten than to loosen. Also, tighten the left adjuster first and then the right one, again in small amounts, evenly.
Re tighten the rear axle nut and replace the cotter pin and you are good to go! If you don't have a tape measure, what works well is a coat hanger ( the wire kind), straightened out with a 90 degree bend at one end. and about 1/2" to 3/4" length after the bend,and a pice of zip tie at the other., you find a point on the frame which is identical, on both sides ( such as the center of the swing arm bolt, and place either the zip tie end, or the 90 bend end there. and the other goes on the rear axle.. its cheap as pretty accurate as well
