Changing the oil

[MikeN]

Thanks Snowbeard.
To paraphrase Roy Scheider in "Jaws": 
"I'm gonna need a bigger funnel!"
Mike.

[BSA_54A10]

While the wear happens where parts actually rub they end up leaving little shoulders on either side, these break off to produce visible swarf as will little bits of threads. Hard faceing can come loose and flake off and the spigot on the bottom of the cylinders can crumble a little at the edges. Slightly larger bits can break off the bearing cages.
Then there is all the flotsum & jetsum that seems to be sucked into the engine every time you open it up. It is amazing just how long little bits of crud can take to eventually end up in the sump.

I had a cage let go at one time and despite having it apart several times including flushing out the cases a couple of times with a few gallons of kerrosene ( parrafin to some)  rivets "magically" continued to appear in the sump for several years.

So a small amount of visible metal in the sump is not a big deal.
What you need to look out for is this volume of swarf stadily increasing which is a sure sign that something is likely to let go or has already gone and is slowly crumbleing away.

An A65 that had the main spin in the cases yielded enough metal to cover an Australian shilling ( about the same size as a US dime )  with every oil change and it did this for three years before I finally decided that I was pushing my luck too far and retired the bike .

A WDB40 that I owned had a cage on the big end roller break up and slowly fall out over a period of 18 months so the weekly oil changes contained a lot of visible metal although this engine did sound like a shaking can of bolts at low revs because the now uncaged rollers would bunch up at low speeds allowing nearly 1/8 " of free travel of the con rod , yet another of the same model did the same thing but this time the bits did not fall out and got hammer welded to the journal and it locked up solid in no time flat.

The 4 way oil filtering system that BSA designed was not an accident. The gauze in the sump will only pull out lumps of metal that are too big to travel through the scavenge side of the pump. The smaller bits get pumped back into the oil tank, but the outlet screen is 80% smaller than the scavenge screen so these bigger bits, which would damage the delivery side of the pump get trapped in the oil tank as designed. The finer still bits of crap get centrifuged out into the sludge trap and the metal particles in there are usually so small that you need a strong glass the see them.

[BSA_54A10]

That is why all these listees who actually know how the system works make the effort to suck the crud that is below the outlet filter out of their oil tanks and you would be well advised to do the same.

The other thing that was not mentioned was when to change the oil.
The answer to this is immediatly you return form a long ride , not after 5 minutes warming the engine the night prior to the long ride. ( same applies double for chains unless you are going to take it off & do the job properly) .
Pop the bike on the stand then drop the oil straight away while it is hot and as much of the crud as possible is floating around in the oil tank. Ten minutes latter is too late unless you are going to do a suck it dry oil change as by that time all the fine bits that are heavier than the oil will have settled  out to the bottom of the oil tank ( which is how it was designed to work) .

Now you know that your bike has 3 filters & a settleing tank you know how much creedance to give to all those wallies that wax lyrical about how BSA's do not have proper oil filtering and imply that the strainer is all that there is.
Having said that there is nothing wrong with fitting a spin on oil filter and in fact I recommend that every one considers doing so seriously but far more important is very regular changes of the oil particularly as we do not use our bikes very much and the oil ends up being contaminated with water & combustion acids long before it's change by mileage.

[bsa-bill]

Just in for a coffee and read BSA_54A10 mail above, couldn't agree more re the filter comments.
My plans to get so much done now I'm retired don't seems to be working, Garden takes priority today ( so I'm instructed ) might manage to sneek a coat or two of primer on the front brake though   

All the best - Bill