[Flip]

They're all a bit rubbish really no matter what bike it is really and I wouldn't rely on the stamp marks in the Swinging Arm to be the same both sides either (take note all those people who think their bike feels better in one direction compared to the other when cornering!).

The only accurate way to do it properly is to use two straight edges from the back wheel measured an equal distance from each side of the front wheel and parallel to it.

Of course all this takes a bit of time and there's no way any manufacturer would ever say their chain adjustment marks aren't accurate and would want to supply a couple of bits of straight material with every new motorcycle they sold.