Good news, I was actually wrong - it didn't shear. I dragged it out of the shed yesterday, and gave it a few pulls on choke. Went 3rd go and stalled, then kept going after that. Was able to go straight off choke to idle with no sign of any timing issue.
I am glad that a week of petrol sitting in the carby (98 octane) seems to have cleared the blockage, but I will probably tear it down anyway.
Regards
Tyler
