Similar problem on son's MB.
I know the manual says he can be done in situ but...
how do you get the crank pulley off when you can't get to the flywheel to stop it turning?

Later...
Tracked down some new pistons, cleaned up rust, painted externally with caliper paint, put in kit.
While it was apart I got Quadrant to rebuild the struts and replaced the rear dampers.

What's involved?

Been working on the MB brakes and have a small amount of rust on the 'dirty' side of the pistons. Any suggestions? Fix or upgrade?

As long as you have a vacuum line between the carb/manifold & your vacuum advance pot & another to the vacuum pot on the secondary throttle the other barbs can be either linked in via 'T'-pieces or blocked. Thanks gadj. No hose on the vacuum advance pot on driver's side of dizzy. No obvious...

I have just acquired a Mighty Boy.
The vacuum advance has been disconnected. The hole on the drivers side of the intake manifold is plugged.
Please could someone tell me how it should be plumbed to work again.
Thanks.

From what you have said, I'd be taking it to the local Carburettor shop and getting it repaired or replaced. Make sure you have a decent fuel filter to stop the impurities coming from the tank and lines. Consider flushing the tank and resealing using something like the Fuel Tank Repair tank PPC Coat...