[jclark]

/quote
I was thinking simpler than that - it's safer to fill to the middle of the sight glass to prevent overfilling should there be oil trapped up in the cooler. The bike doesn't need the oil level right at the top of the red circle, and doing so just risks overfilling the engine.

But I like your reasoning better. Sounds more technical.
/unquote

Um, well, I think the idea is that one doesn't accept the veracity of the sight glass, without first being *sure* that the engine has been thoroughly temperature cycled ( determined by feel - the oil cooler is just as hot on the sight window side [ right hand side looking at the headlight ] just touch the bottom of it - if you can't touch it for more than a second, your prolly all right.
Then park it on it’s side right away for, oh, 10 minutes or so, put it on the center stand, and look at it in the morning. If you look at it after only 10 minutes on the center stand, the value will be off by the amount of air mixed in with the oil - after an overnight ( well prolly sooner, but that’s not where I’m headed ) sit it will all be settled out.
And reasonably accurate.

jeff
...my finger hurts....