Best thing to do is put fresh oil like a ISO 46 oil in the one shot reservoir and start pumping oil until you see fresh oil come out at the oiling points. That means, the oil turn from a very dark color to near clear fluid like. Do this until all oiling points show clean oil. Once that's done, fill the reservoir with your flavor of way oil. It means a lot of oil waste, but is the easiest way doing so. That way, if you encounter a oil line that does not deliver oil, pull that line and replace. It is difficult to get a oil line unclogged sometimes. I have a air nozzle fitted with a fitting that adapts over to the Bijur oil line fittings. What I'll do is connect the oil line to the air nozzle and attempt to use compressed air to unclog. Just be sure to point the oil line away from you when you shoot the air to it! If nothing comes out of it, don't look at the muzzle end of the oil line. It could come out and blow your eyeball out and if the oil was to get in your blood stream, kill you. So be careful! If there are metering units, that regulate the flow of oil, in line and that's where the oil flow stops, remove and replace the metering unit. They are a hit and miss trying to clean and get them to flow oil thru once they are clogged up.