chain

[AK400]

how much play should there be on a 400ex chain with out someone sitting on it??

[GPracer2500]

1 1/4" to 1 5/8", on the upper run midway between the sprockets.

I've always found it to be a good idea to check the slack, then turn the rear wheels 1/4 or 1/3 of the way around and check again. Turn, then check, etc. If the chain and or sprockets are worn unevenly or the rear sprocket isn't perfectly centered on it's carrier you'll wind up with a tight spot and a loose spot. Set the slack at the tight spot--unless there's a huge difference in slack between tight and loose. If that's the case, the tight spot vs. loose spot issue needs to be addressed first.