It could be a issue with the Reeves clutch drive, so take the cover off and lubricate the shaft with some dry lubricant like PTFE spray.
After which, it might be worth chucking up another piece of wood and giving it a manual turn to get going, while messing around with the speed while your at it.
Chas, or CHJ has wrote about this here before.
Edit: it looks like this machine has a manual belt change for speed adjustment
Failing that, capacitors are a the price of a pint, so if buying another look for the uF "like" symbol
which is the micro farad rating.
You can buy any one which has the same value, but make sure its the same dimensions if it needs to fit into a terminal shroud.
Good luck
Tom