I don't understand how than my chain will be overtightened....
It will be OVERLY TIGHTENED because you are NOT following the instructions in your OWNERS MANUAL.
At the point that all THREE CENTERS are IN LINE, effectively you do NOT need ANY SLACK in your chain, so when set THAT WAY, then you check slack w/ the V on its side stand, you will end up w/ 1.0 - 1.4" slack. THAT IS THE METHOD KAWASAKI USED TO GIVE YOU THOSE NUMBERS, and WHY they detail that method to check your chain.
...Also I ride relaxed, no hard acceleration, so my chain are not in big stress, so it should last long time.
IF your chain is OVER-TIGHTENED it will NOT matter how "relaxed" your acceleration is - your chain WILL fail!
Back in '09 while I was riding to Alaska on a KLR650, I adjusted my chain one night, but FAILED TO RE-CHECK AFTER I TIGHTENED THE AXLE NUT
, then the next day I departed w/out rechecking it - it was overtight which I noticed at the gas station down the road as it was VERY difficult to 'roll'
so I loosened the adjustment, but it was TOO late - my chain was already 'spitting out' rollers, so the chain was SHOT, and I ended up changing the chain that night INSTEAD of going for beers w/ my riding buddy!
Take my word for it - TOO LOOSE or TOO TIGHT WILL
ruin your chain, and IF it breaks it can destroy your engine cases as well
, requiring a NEW engine.