Hi I have a 1955 road rocket.A10...I decided to freshen up the bike with new bore,piston, rings,valves. I've recently discovered information about the sump trap and details about it and the use of detergent/non detergent oil. My question.if the sump plug still has the dimples at the threads and looks original,never removed, should I continue using non detergent oil or risk releasing a lot sludge into the oiling sytem by using detergent oil.??
Hi,
When you say 'sump plug' do you mean the sludge trap plug in the crank?
How many miles has the engine done and have you been using detergent oil already?
Dave.
Hi,
If your bike hasn't got an oil filter its better to use oil with detergents/dispersants. Change the oil at 250 then at 500 miles running before returning to the normal service period. However your engine noise levels will slowly increase as the microscopic particles slowly remove from the casings into suspension in the oil.
Best wishes...
You mean it's better not to use detergent oil with no filter. Detergent oils are designed to keep the rubbish in suspension until it can deposit it at the filter.
Engine noise increases because mineral oils are non Newtonian, after being subject to sheer stress and heat the viscosity modifiers cease working, your 20-50 is now just a 20w. However with regular changes or a v-twin oil.
Hi Allan,
Nope I stand by my statement - If your bike hasn't got an oil filter it's better to use oil with detergents/dispersants. It's always been a misconception the other way around.
Combustion solids are microscopically small and if they are allowed to grow they'll become a size to damage an engine before they are large enough to settle. If particles are allowed to grow they'll become a size which will adhere to metal surfaces and over time become big enough to see and settle. While the solids are microscopically small they do little damage, so oil has dispersants and with detergents stop the particles from adhering and accumulating to surfaces. Using an oil with detergents/dispersants and carrying out oil changes in line with the manufacturers recommendations removes the suspended solids.
The engine noise decreases due to the insulating effects of solids adhering forming thick grey/black grease like substance on the internal casing.
BSA knew this that's why they published a service sheet 81, attached.
Not sure you are right in your second paragraph. I believe oils are Newtonian because they do not vary with shear or strain. They become non Newtonian after thickened with a viscosity improver (polymer chains). True these chains break under shear caused by such things as roller bearings, but don't affect engine noise as much as clean engine casings. I don't notice the change in volume if using a straight oil which is Newtonian.
Best wishes...
p.s. - Also, if you got an oil filter it's better to use oil with detergents/dispersants :)
A Newtonian fluid can be compressed or strained but will return to its original state, synthetic oils have this nature, oil passing through the journals are compressed until they find their way into an unstressed environment. Water is a good example. You can boil it and collect the condensate but the viscosity will never break down.
Mineral multi-grades are non Newtonian, they will accept a certain amount of sheer stress but eventually with the application of heat and moisture will break down. A 20-50 is a 20w oil with viscosity modifiers (aka additive pack) when the additive pack starts to fail (which it will) the oil returns to being a basic 20wt oil. Things start to get noisy quickly when the oil cannot hold a decent viscosity but also wear increases on the component (goes without saying) I've found this when running the bike during very freak hot climate. The bike was noisier until the oil was replaced.
Going by that 1961 article I've seen 1970 bikes with heavy sludge, I've also seen other bikes that haven't there's never been a change in top end noise because of this - regardless of the very outdated oil regarding Dino oil.
Hi Allan,
Crane engineering say different.
Best wishes...
The 20w base stock is Newtonian but the mineral oil additive is not. Or rather it has non Newtonian properties.
Regardless of this, detergents in oils were designed to keep the fluid in suspension until they could reach the filter, in the case of the bsa it was a centrifugal filter know as the sludge trap.
However, back to the posters question (before we spend all week picking sections of text which we wish to make comment against instead of looking at the whole text)
As the condition of the motor is something that concerns you then you would not go wrong by stripping the engine, checking the sludge trap and the condition of the journals and shells. If the sludge trap is plugged this will eventually restrict oil reaching the big ends. By doing these checks you might incur an initial cost of at least a few gaskets or at worse find you need a regrind (a 2" micrometer will become your friend), if it is bad and you ignore it you could end up putting the rod through a Case
(Worst case scenario) destroying your rod, cylinders, crank cases and crank. If you can see a level of black sludge from the crank case mouth, then it's a good place to start.
Hi Allan,
QuoteRegardless of this, detergents in oils were designed to keep the fluid in suspension until they could reach the filter, in the case of the BSA it was a centrifugal filter know as the sludge trap.
The sludge trap was adopted before BSA specified oil with detergents/dispersants. It is there to centrifuge the insoluble sludge formed due to the lack of detergents/dispersants.
The detergents/dispersants will keep the solid particles microscopically small, most of these will pass through a full flow filter (30 microns) and stop it clogging. If you fit a partial flow filter (10 micron) you will capture more but you're only filtering a proportion as some oil is by passed.
Perhaps a published piece will convince you?
Going back to the original post I still feel:
If your bike hasn't got an oil filter its better to use oil with detergents/dispersants. Change the oil at 250 then at 500 miles running before returning to the normal service period. However your engine noise levels will slowly increase as the microscopic particles slowly remove from the casings into suspension in the oil.
Is the best advice.
Best wishes...
Hi Bess
I like the idea of keeping the particles moving around and not getting stuck in the sludge trap or other small oil ways, which oil do you use.
Hi,
This one:
https://www.brandedbiker.co.uk/shop/silkolene-silkolube-20w-50-motorcycle-oil-4-litres/
Best wishes...