To answer your question on sludge traps,,,,YES!!! loads of them clogged up. One of the issues of modern oils is they contain loads of detergents and are designed to keep particulates, sludge, Smegma and swarf in suspension instead of settling out. So typical scenario is a well meaning but poorly educated new owner for a vintage lump (BSA-Norton-Triumph) hauls a treasure out of a shed, barn, or garage and adds some fluids and then rides it like they stole it.
Not only has the sludge (Just like a sewage septic tank) probably plugged up the bottom end while sitting but it then gets stirred up and recirculated thanks to modern Oils,,and running thru the bearings and surfaces. Or plugging up small orifices elsewhere in the motor.
Yes I have this arguement regularly.
People seem to want to use high detergent modern oils which as every one here should now know prevents the tiny particulates amalgamating into bigger lumps and dropping harmlessly to the bottom of the oil tank as BSA intended.
Now these particles do not vanish and if they are smaller than the 120 micron screen in the bottom of the oil tank they then pass through the pump but get pulled out by the full flow centrifugal oil filter commonly called the sludge trap.
This leads to the common misconception that detergent oils clean the engine because the sludge trap fills up very quickly.
