I've just built up my nc after replacing the sprocket seal. I'm running a hose pipe into a catch bottle from the oil breather. It seems to be blowing out more air that before, although i'm not 100% sure. Its a race bike and running ramair.

I took the oil filler cap off when it was running and theres a fair bit of air coming out.

Just like to know is this normal and i'm i getting worried over nothing.?

if you run it with the oil filler off then it should pump air out of there - the downwards pistons have to shift the air somewhere and usually it is inside the crankcases and this is why they get pressurised. I imagine if the seal was replaced then the pressure cannot get out of there and so rightly is coming out the top breather. Some guys fit a hose to the filler cap too - this will allow the cases to breathe better still.

So, it is normal :) IMO anyways!