Saving Old Seagulls

There are lots of offers of compression testers around. But do any of them fit a Seagull head? I suppose what I'm really asking is, is the bore and thread of a spark plug hole so standard that, even after the move to the metric system, it remained the same?

If a specific fitting is required does anyone know what it is please?

Thanks.

I use one similar to this one and works perfectly well in any seagull.
It also has adapters for smaller or larger plug holes so plenty of options.
https://www.ebay.co.uk/itm/Draper-37442 ... Sw8RZaYJRT

Jon

Thanks for the reply Jon

I guess that you use the 18mm adaptor? I know that 18mm plugs are used in Seagull heads but surely the measurement does not refer to the thread and pitch of a Champion D16 (for example)?

A D16 has an 18 x 1.5 mm thread, as do all the classic seagull spark plugs.

Thanks Charles.

Ebay thread adapter. I have one of these.
I was going to make one but for £3 odd it wasnt worth setting up the lathe.