Quote Originally Posted by T 20 View Post
No idea on the Airsporter yet, Tone, but what I can give you are the standard Mercury dimensions :-

Cylinder Bore X Stroke = 28mm X 65mm (1.1" X 2-9/16")

Piston weight = 320grams

Transfer Port = 3mm X 11.2mm

Available Spring room when cocked = 110mm


The only difference on my rat gun are the stroke at 70mm and a piston weight of 314 grams.

The spring I removed was a 33 coil Spring with 3.1mm wire.

Another problem which showed up was the fact that the end wall of the cylinder has a hemispherical section machined from the centre of it.
I don't know if this is supposed to be there or is a machining cock up at the factory, whichever it is it creates a little more work as I'll have to make a P38 casting of the cylinder end wall and machine the piston head to match.

That's about as far as I'm going to get today while I stare at the piston and think about the job, but I have a good idea which way this is going to go --- new piston.


All the best Mick
Excellent information as always, Maestro.

Maybe nice to post those vital stats in Brucie's Bore, Stroke & SCR thread, if you don't mind?

Nicely enough dimensioned TP, methinks?

Hemispherical section in the cylinder end (head?) - does it think it's an internal combustion engine? Maybe this was where the term "dieseling" originated from?

Hope you get that addressed. Correcting that lost volume should improve efficiency no end.