Quote Originally Posted by TonyL View Post
Ah, a very useful re-purposing of a BSA (style) part then?

Is the idea also something to do with stroke gain, Mick?
There's basically three reasons behind my thinking of using an O ring, Tone.

First off the piston isn't the best I've ever seen so making a bronze piston head with O ring will keep it centred at the front end.

Secondly, the leather piston seal is 8.5mm wide and the cocking lever slot has 3mm of clearance, so if I make the bronze head 6.5mm wide this still gives a 1mm cocking slot clearance and will increase the stroke to 71mm without messing about with the back end of the piston.

Lastly, bronze weighs more than steel per cc, so with a bronze piston head I'm adding weight to the piston without robbing any Spring room.



I may be going off in completely the wrong direction by increasing the piston weight but I reckon it's worth a punt --- I'll have a better idea which way to go when I've stripped and measured my ratting Mercury this morning.





All the best Mick