Hi Adrian. Whoops, or a similar expletive. Sure its not left in gear in the confusion? OK, clutch disengaged, kickstart moves, mainshaft and layshaft are free.
As a start, whip off the sump plate. A good cup of oil should be in there. Full to the brim? Hydraulic lock. Dry as a bone? The engine has probably seized.
Get the primary cover off, and remove the clutch springs. This effectively separates the engine and gearbox and if you find the crank now moves OK, then the fault is in the clutch.
Crank still solid? Carb could have put neat fuel into the bore, washing off the oil, so see if the pistons are seized in the bores by lifting the barrel which may allow the crank to move and turn slightly. Pistons moving OK in the bore as the barrel lifts but crank still locked solid? Good chance the timing bush has seized on the crank, a big end seizure or the camshaft is locked up. Something as simple as a jammed cam follower could do this, so if pistons and crank move normally with the barrel lifted an inch or so this is where to look. Seized rockers possible, easy to check but unlikely. No need to take off the head yet for these simple checks. Jammed or seized timing gears are again possible but unlikely.
Be methodical, but as it stopped without any major clank or bang it will require a bit of detective work to find the fault.
Swarfy.
