RichardL asked for an opinion on the Sludge Trap...so here are a few thoughts.
Crank failure due to poor oil flow to the left hand B/E caused by a blocked trap can be relatively minor, or an engine exploding wallet busting disaster. Either way the dilemma remains of trusting to luck or going straight in for a complete strip on any unknown engine.
Certainly these motors are relatively simple and my guess is that most are not used daily as a primary means of transport, so could be fettled completely without too much inconvenience. Certainly a strip and clean before disaster strikes is cheaper and gives peace of mind.
But it could be argued if the bike runs OK, leave well alone and use non detergent oils. If it fails meantime, then it has to come apart anyway. But now you've got the increased cost of any damaged parts and the hassle of finding maybe rods, crank, cases barrel and pistons.
From experience the lubrication through the early crank is poor in standard form, an end fed crank is better, big journal cranks are better still, with bigger oilways and improved trapping capacity. So worth doing, also knowing all is well takes away some of the uncertainty of will it make it home?
So I'd go for a stitch in time.... sooner rather than later, but in the short term encourage the sympathetic running of a new bike as it is also allows other problems to be identified and the whole lot can be done at a convenient time.
Swarfy
