Tightening or Loosing the chain
1) There is one pivot bolt which holds the H shape axle frame (H-Arm) to atv's main body frame. Check this first to make sure the bolt is tight but still allows for up and down movement. This pivot bolt keeps the H shape axle frame and the main body frame in alignment.
2) There is 4 bolts (2 top and 2 bottom) at the the back atv that moves the axle. You will need to loosen those 4 bolts so you can move the axle back and draw tight the chain. Make sure the axle is straight (align straight with the body) and the chain runs straight. Also, If one side or the other side are not tightened (the 4 bolts) the chain will fall off again. Also if the rear end is not straight then the chain will also fall off.
3) The Proper chain tightness is when the chain is snug not allowing it to flog up and down (please not to tight)
4) Some chains came too tight & cannot be loosened by adjusters because they are as loose as they will go, so a master link will need to be added to lengthen the chain.
To Lengthen chain take it apart and lengthen it by adding a master link on it. You can get the master link at a local hardware store or bike/atv shop.
To Shorten chain take it apart and shorten it by adding a master link on it. You can get the master link at a local hardware store or bike/atv shop.
Chain continues to come off
1) Remove the chain
2) Jack up the atv under the engine motor mount area until the rear wheels come off the ground.
3) Then see if the H arm (rear) moves back and forth about 1 inch to 2 inches. If the rear H-Arm moves back and forth, then the rubber grommets inside the top of the H-Arm (going left to right are shot/bad. The Best way to fix that is put in a metal pipe that acts as a bushing (replacing the rubber grommets).