Josh-I think you misunderstand the purpose of the sludge trap. In your post, you talk of using oil mineral detergent to clean it out-I assume you mean with the engine running? NO! don`t do it-will mince your big ends. Its called a sludge TRAP for that very reason-it traps any sludge present in the oil that is being pumped through the crank and thus PREVENTS it (the sludge, not the oil)from passing through the shell/journal gap.Thus we should only get clean sludge free oil at the big end bearing surface.If you loosen all that crud (accumulated over years/1000`s miles) with detergent it will all be forced out through the b/e bearings and trash them in an instant.The only way to clean out a (BSA)sludge trap is to strip the motor and clean it by hand.....
A little on how the sludge trap works will be useful: In the A10, the trap is a thin walled metal tube about 1/2"bore dia.It has a step up in that diameter at the "feed" end to about 3/4". There are two small holes halfway along the tube, these holes are where clean oil emerges on its way to the b/ends, and another single larger hole diametrically opposite the above pair (for the locating bolt).When the trap is correctly mounted in the crank, the two small holes from which the oil emerges are positioned so they face inwards i.e. towards the crank centreline/axis.The principle of operation is : the trap is mounted in the centre of the hollow b/end journals in the crank.It is concentric to the big ends, but of course is not on the axis of the crank itself.Oil enters the sludge trap tube directly from the pump,at the larger diameter end,(the larger dia end matches the bore in the crank itself and prevents any oil sneaking past the trap and by-passing it, thus this fit in the crank here should be close).As the oil enters the trap it is subjected to high centrifugal forces due to the crank spinning, and is forced outwards, gathering along the back of the sludge trap wall, at the opposite side to the two small holes.Any sludge/debris in the oil is thus "pinned" against the back wall of the trap tube,away from the two "exit" holes.The trap tube fills with oil,which is forced by sheer volume out of the two exit holes(against the centrifugal forces) into the crank journal leaving behind any crud "trapped"in the sludge trap..More later, Bob