Lubrication
Oil CirculationWhat oil to use?
Where the oil goes
Oil Circulation
Lubrication system
What oil to use?
The Nimbus engine is 'wet sump' - there is no separate oil tank. The gearbox shares the oil (also fed under pressure). The engine also runs with very slightly negative crankcase pressure - meaning the inside is trying to suck air in from the outside - which serves to reduce any oil leaks.
Check the level in the sump every day you ride using the dipstick.
The dipstick is (normally) marked with 2 levels - see the picture below. At maximum the maximum level mark, around 2L of oil is held.
Dipstick High & Low marks
Change the oil every 1000 to 1500 miles - oil is cheap compared to engine re-builds.
It is recommended that you use a non-detergent single grade oil. 40 grade (I use 50 grade in summer).
The engine is filled by springing-back the vent tube - revealing a massive hole for filling with oil (Moto Guzzi owners eat your heart out).
Oil filler cap
Multi-grade detergent oils (20-50, etc) would probably be fine on a newly-rebuilt engine - but on an older engine, the oil additives will remove carbon particles and gums, which could eventually block small oil-ways. Don't be tempted to use the very thin multi-grades around these days - such as 10-40, or even 5-30 - these oils are designed to work in water-cooled engines.
Oils are good these days compared with when the engine was designed - so perhaps oil choice probably isn't anywhere near as difficult as it used to be.
Where the oil goes
An important thing to know is that the oil to the cambox feeds and returns through one pipe. Or at least it looks like one pipe (it's actually one inside another). If you have to remove this pipe, make sure the gasket is in good condition, and not cracked or has a piece missing. It could well lead to an oil 'short circuit' - so that little or no oil gets to your camshaft.
See the oil circuit diagram above to see how the oil gets around the engine. It doesn't show that the inlet valve guides are lubricated by oil vapour sucked from the crankcase by the carburettor. Exhaust guides are manually lubricated with a drop of oil from a can 'every now and again'.
Cambox oil feed
Back to Technical ToC Top of page
