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J2 engine

Paul Potter

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There is no sump plug on the J series, I used to remove one of the crankcase doors, the 3rd I think, on the port side  and remove the old oil using a can or old garden syringe, mopping out the last remains with a cloth. It’s a mucky job! With the sump empty, the brass gauze strainer is exposed and can be removed for cleaning. Refilling is via the same removed door, keeping an eye on level using the dipstick on the other side of the engine. Once full, I rarely needed to top up as oil from the dashpots on the heads maintained the level, or raised it slightly. Happy to speak if I can help further, PM me for numbers.

Lovely motors, Kelvins!

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On our J2 I find the aft, port side crankcase door gives the easiest access, but be carful not to damage the oil test cock.

A Lidl oil suction pump makes quick work extracting most of the oil, then finish mopping out the last dregs from the sump with some lint free rag.

Used engine oil is toxic, so be sure to use suitable gloves for protection.

Don't overfill when topping back up.

I was recommended to use Morris Golden Film SAE 30 classic motor oil - needs to be a low detergent/dispersant monograde lubricant (Other oils are available).

Have you got a copy of “The Running and Repairing of Model J”?


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Get the oil out, as above, them scrape out any carbon mud in the crankcase with a (unwanted) dessert spoon.  An occasional rinse round the corners with a paint brush and some diesel does no harm either.  Periodically check the strainer is clean- wash it in diesel/kero.


Change the gearbox oil at the same time.  Drain plate is below the shaft at the back of the box.  Refill (1 1/3 pints) throuh the plate on the top of the box.


Refill the sump through the filler which is the sloping pipe, central, on top of the crankcase, at the flywheel end.  The book says the sump holds 10 pints.  On mine that is way above full on the dipstick, but the level  is clear of the balance weights and it does not smoke, so I run like that.


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