Oil Pressure ?

[stunva]

I changed the oil on the Hayabusa today and noticed two things, the oil wouldn't drain out quickly unless the oil filler cap was out, I thought funny but fair enough. Then after I was finished the change and ran it for a while and went to top it up as the oil filler cap became loose it sucked air in like there was a reasonable vaccum there, is this normal for the Hayabusa, I've never noticed it on any of my other bikes.

Stu