I don't have this bike here as of yet , so I don't have any clue as to what kind of head it has........Perhaps Brian can shed some light on what his one has....... STT 28.
This one could be a little tricky. Cracks radiating out from the bronze combustion chamber through the aluminum."Skull heads" were pretty common back then.......Norton for one used them........Large bronze center with the alloy fins cast over it all.........interesting concept.......must have been tricky.
Yes good question... I was surprised to see that cracking... haven’t seen it before, but haven’t seen that many bronze skull heads. This one needs the intake seat repaired, but machining for a seat insert isn’t a good idea because it would partially intersect the head/cylinder mating surface, so I think TIG is the only option.That "skull" is huge, so no surprise that the head developed cracks, not a lot of aluminium around it, so it seems. The Laverda type is much smaller in cast iron, but then you can see the effect of deep sitting valves from reworking seats many times. Big question what to do in this case ?
Vic
Laverda head
AJS Porcupine. Actually, they explored the idea but it was too expensive.I seem to remember that the Velo"porcupine" heads were cast in Silver
The worm drive clip is called a Jubilee clip in the U.K. and was invented in 1921.Note the worm drive clamps used, in the pictures posted by David. Someone on a car forum was commenting on how a car from the 60's would never have had that type of clamp, as they weren't available in the 60's???