I have a1960 wideline coil ignition ES2 which in general gives me no trouble. About 3 years ago I halted at a friends and the machine stopped very quickly when I turned the ignition off. I went to start it about half an hour later and it appeared to have seized so I had to recover it with my trailer. Upon stripping I found nothing wrong.
This experience seems to occur about once a year now but I have learnt that it is simply “lock up” whereby the machine seems to stop at TDC or BDC, not sure which, and the way to rectify the issue is to remove the spark plug and bounce the bike down a slope in third gear to release the piston from its top or bottom dead centre. It is impossible to move the piston by utilising the kickstart only.
Am I alone in experiencing all this? It doesn’t appear to have been mentioned in any of the Singles forum before. It has never occurred with my Inter in 18 years ownership.
Have I got something wrong somewhere? It all has just happened again yesterday.
I had a similar problemon a model 50 which turned out to be caused by end float in the crankshaft allowing the big end nut on the drive side to come into contact with the boss of the main bearing in the crankcase side
I was speaking to a friend today who reminded me that he had experienced a similar crankshaft lock-up on his 1950 ES2. Could only be freed off by applying a spanner to the engine sprocket nut. That engine went away to Mike Pemberton for an overhaul plus performance mods. Mike reported that it looked as if someone had replaced the big end bearing but had failed to press the flywheels fully together and didn't tighten the crankpin nuts properly. This left the crank assembly wider than it should have been and the timing side flywheel was striking the camshafts.
I'm not sure how far you stripped the engine but I would recommend taking a closer look at your crank shaft assembly.
Cheers, Ian McD