as above - upto 1 lite of oil per 600 miles is normal - and thats when new

open your airbox lid and see if the brerather is chucking loads of oil back up the pipes into the airbox - you couls help matters by fitted a decent breather system, but as aboive also, if its got excessive blowby on the rings, you really need to get that sorted with a rebuild, but if u are not too bothered and just want it to run till it dies, geta breather system fitted.