Hi Mosin,
Sorry to hear of your calamity!!!
Looking at the nut it is the early type, I am/was under the impression that the castellated nuts were only used
on the early models,
Any engines I have worked on have the self locking nuts????? and I am assuming your 1960 bike should have the later type!
Of course WTF do I know?
Reading the other replies reminds me, a couple of years ago my Son David bought a 1952 Ariel 350 as a non runner
It kicked over ok and had compression, I persuaded the mag to spark and David cleaned out the carb, I told him to remove the sump plate for a look!
He did this and a 5/16 cei deep nut fell out,split vertically in 3 pieces
WTF did that come from? as I know such a nut does not belong anywhere inside the Ariel engine!!
Anyway we decided to see if the engine would start after replacing the sumpplate etc
It sounded like a bag of nails when it fired up
David found a replacement engine on fleabay that turned out to be a cracker, the seller replaced it with a 650 Huntmaster unit!
Then recently I was approached by a chap who was looking for an Ariel 350 engine or bottom end to build a spare for his pre 65 trials bike, I offered him the rattly motor making sure he knew it was knackered,
he offered a good price for it
as he only wanted the casings and rocker boxes etc
Something like that has never happened to me before, I'm always the poor sod who buys something only to find out when I get it home,
A, its the wrong part
B, its knackered
C, its wrong and knackered
I will disagree slightly with Beezaalex in that if you had the TS conversion done any dodgy issues would have shown up when the engine was being rebuilt!
Best Regards
John O R