Clogged oil line, faulty oil pump, incorrect oil specification (not another oil thread....), etc... a mix of these.... Half a liter is the volume between Low and High oil level in the dipstick. Running at low level is not bad. Running below Low level is bad and can cause oil starvation. I try to keep between L / H, but i've noticed at low level my 950 did not make any unusual rattling, but these bikes have a tendency to behave differently on each specimem.... carefull not covering up a problem with a temporary fix such as adding oil. Somewhere along the way, KTM superseeded the CCT bolt, with a longer one (+/- >3mm long) that made measuring the distance to the cylinder wall slightly higher than with the original bolts, keeping the distance between 6 and 11 mms, thus rulling out the need to replace camchains. Here My 05 950 had the smaller bolts, your's is a 04....i believe its part 60036008100. Precisely! From what i've been learning with this great bike, always start from the far simplest, stupidiest simple possibility, and then rule out accordingly until you get to the weirdest, far fetched scenerio ever imagined... And always be ready to stand corrected.