The Achilles heel of the A10 lubrication system (or for that matter many other bikes)seems to be the sludge trap. With the advent or modern detergent oils and the fitment of external oil filters could the sludge trap be omitted? In by gone days before efficient filtration was readily available the sludge trap was a crude but practical way of removing damaging debris from the oil, but of course it has one major flaw. Eventually it blocks up and, at best the bearings fail and, at worst catastrophic engine failure occurs. For instance I run my engine on 20/50 fully synthetic oil. You can read about the oil that I use here:
http://www.fuchslubricants.com/comp-4-20w-50 Personally am very pleased with it. This oil is relatively expensive, but I work on the premise that oil is far cheaper than engine rebuilds. There are of course many people that continue to use the original spec mono grade oils for all kinds of reasons. A frequent criticism of 20/50 oil is that it causes engines to leak. That is not my experience however. This article makes for interesting reading
http://www.realclassic.co.uk/techfiles/oil030319.html written by a guy that spent his entire working life in the oil industry. The general consensus seems to be that a filter should only be fitted to the return line on our engines. The most frequently stated reason is because if the filter becomes blocked then the engine will be starved of oil. Fair enough, but isn’t that exactly what happens with the sludge trap? If the oil is changed at regular intervals I would have thought that the probability of a full flow filter becoming blocked is very unlikely. BMC A series engines used to have an in line oil filter on the delivery side that incorporated a by pass that allowed the oil to flow unfiltered if for any reason the filter became blocked. Should this happen a warning light came on indicating that the oil filter was blocked and needed attention. Quite possibly the Mini filter head could be adapted for use on a bike? Having said that I am not aware of any problem with filters blocking on car engines on a regular basis. Maybe there is a problem with a difference in oil pressure between a car and a bike. Having said that the filters used for bike applications are often sourced from filters originally designed for use in cars, so I cannot see why there should be a problem. Maybe someone with a more technical automotive back ground could expand on this? It does seem to me that given the importance of keeping the sludge trap clear to maintain a healthy supply of oil to the engine that it is, at the very least highly inconvenient because to do this it requires a full engine strip. Of course another problem is that it impossible to monitor the state of the sludge trap to see if it requires cleaning out!
It is interesting to note that the BSA / Triumph triples were not fitted with sludge traps, ( the crankshaft design rendered this an impossibility) and that the oil filter was fitted to the delivery side. Neither was there any by pass facility provided to protect against filter blockage. Not only that, the recommended oil was 20/50. Remember that like our A10’s the engine was air cooled, and was basically a Triumph twin with an extra cylinder added on! I thought that I should just add that I change my oil at 1000 mile intervals too.
