Searching previous posts where people have touched on this subject has not revealed that anyone has ever come across the use of Royal Enfield pistons in their engines.
My spare engine is fitted with what appear to be 350 Royal Enfield pistons of a type that were only made between 1948 and 1958. They are stamped as being +20 and bear the marking HEPLEX 11250.
One of them has plainly picked up badly in the past and is really not fit to go back in the engine.
I thought I had struck gold when someone located a NOS Peter Hepworth piston which is identified (on the box) as a Royal Enfield 11250 .7mm STD = 69,874 + 0.7 mm.
However, although the usual dimensions are the same it is not the same as the pistons which came out of the engine -
(a) It has a solid skirt - whereas the old ones are split skirt
(b) It has three rather than one rib under the crown, and
(c) It has a very thick rib around the inside circumference of the skirt.
All this and it is 25 gms heavier than the others! Vibration Free do not think that it is feasible to reduce its weight to anything like an appropriate degree to match the others. They can get a bit closer by juggling the rods and pistons but are reluctant to start removing metal as they can't see a satisfactory outcome.
Hitchcocks Motorcycles have a splendid selection of RE spares including pistons which would fit but the crown is higher and they have slots for the valves which on the RE 350 are at 90 degrees to where they are on the Augusta. I am not currently prepared to invest £100 in a piston and have someone take a chance on machining the crown unless anyone has experience of doing this - succesfully!
Any ideas gratefully received as ever!
