Ancient ATCO rotovator drive box.

Hello Folks,

As my login will suggest my mate & I are fairly new (2 years) to an allotment, however we have been gifted a rotovator. Whoo Hoo!

The engine is a Briggs & Stratton 5Hp from ~1945 (according to the engine number etc.) in an ATCO Cultivator Deluxe, however having now got the engine going, it's making some dreadful noises from the drive box.

Can anyone please advise how to clean and lubricate the drive? I cannot see any straightforward means of draining/cleaning what I presume is a chain in the casing.

Thanks in advance for any hints, Cheers, Mal.