Disc or drum M/C how to tell

[YY1]

Is there a way to tell from the outside if a master cylinder is for disc or drums? I found two out in the shed, and might like to use one if it's for disk.

On a related note, I uderstand the internal difference is a valve that keeps some pressure for the drum. Can this be renoved/modified so the M/C cab be used for disc? IE, during a rebuild from a kit.

Probably should just use as a core but I'd like to know.

Thanks much.

 

[yellowdartdave]

Disc brake M/C will have 1 large and 1 small reservoir.

Drum brake M/C will have both the same size.