Small breather hole 30u engine

[1930]

The fresh air vent is in the front end of the crankcase left side thru the oil filler pipe, air cleaner shutter works thru the air cleaner assy.
Hope you can see the bolt head back there, it is with sliding this bolt head that you open or close the ventilation, I would guess that as mentioned Plymouth does not have the option of opening or closing, plymouth is just always open.

[Tinkeys]

Thankyou for picture of your engine , pics are worth a thousand words and helps alot !