Oil filler breather

[muddy]

Been having oil leaks from different places on the chain cover. Just noticed the breather is just about non existant. The previous owner had it chrome plated virtually closing it up. Going to run a drill through it, my question is what size breather hole is normal. thanks!

[MK Monty]

I wouldn't know the hole size but around 2.5 should be OK I would check that it is not an Indian repo one and that it has the baffle plate inside with some form of wire wool stuffing so it breathes and doesn't splash oil out. Seen a lot that are just an empty shiny dome for show

[muddy]

Thanks for the reply I'll check it tomorrow.