well i ride it four miles to work most days and yes it is quite high revs as its geared for off road, it has a 14 tooth sprocket on the front and a 46 on the rear so i do have to thrash it a bit to keep with traffic as i ride along main roads, but at weekends i take it out with a few mates to do some green laneing and don't need to thrash it too much as we plod through back roads and rough terrain, it seems to use the most oil during the week when i commute to work and back.
what kind of plug does your bike have fitted? mine is a wr 400 i don't think the 450 have this problem so much, i have read on a few other forums now and it seems as if this is normal for the 400 and 426 to do this it seems most of them do. im just thinking of ways i can stop this from happening ie a plug of some sort.