Adjusting the chain
You want to have at least 1/2-3/4 inch of slack in your chain. To tight is just as bad as too loose.
With a tape measure...measure from the bottom chain stays to the top of the chain (the drive part). Alway's measure from the same place...I use my chain tensioner as a guide (about a inch and half away from it) Measure in the middle between the sprocket's.
Measure the chain first
Now with your finger pull up on the top chain (drive part) until all slack is gone...As you can see I have about a inch of slack...too much
Use your tensioner to adjust..If you do not have enough adjustment on your tensioner...moving it back (towards rear sprocket) should give you a little more adjustment. If you can't do that...you may have to remove a link. If you remove a link, you may also need to move the tensioner back towards the engine. BE SURE!! removing a link will not make your chain too short!!