Cub Oil

[subira]

Anyone able to recommend an engine oil for a rebuilt trials Cub ? Silkolene Chatsworth 30 has been suggested by another Pre-65er. But its proving difficult to get hold of.

[old trials fanatic]

Hi

I also have an interest in the Classic bike scene (road bikes) and this subject always crops up.

Current thinking seems to follow these lines.

Monograde oils, Chatsworth 30 etc, were appropriate when the bike was new (as that was all that was available) however there are better alternatives now. The reason some people suggest monograde oils and the reason you wouldnt use say Mobil 1 5w 40 is generally speaking older engines were designed with much larger tolerances than modern ones. In fact some older bikes tolerences when new are larger than modern Hondas when nackered. All that then happens is the oil pump can not maintain pressure and the oil just leaks out of all the bearings and some of the mating faces as well. Engine go bang! The other thing about monograde oils is they generally speaking have no detergent properties. Now what this means is they allow the products of combustion to be deposited in the engine, thats why the insides are so black, they do not carry those deposits in suspension. Conversely multigrade oils do have detergent properties and they are designed to carry the products of combustion in suspension to be collected by the oil filter. When i say oil filter i mean the cartridge type of which there are many kits available not the gauze strainer in the oil tank which is there to collect the odd twig (joke). So that really sums up your choice. Synthetics are out (too thin and too slippery). Monogrades are good but not so eaisily available and tend to depost the carbon all around your new rebuilt pride & joy. Best avternative seems to be good old 20/50 eaisily available and if you fit one of the filter kits works perfect.

I and most of the guys locally use (dont laugh) Wilko 20/50 dead cheep under