Balancing a flywheel is always a good idea, but to get the most from this , it should be done with the crankshaft, and front pulley, so the whole assembly is balanced together
It is also important to get the run-out within tolerances as this will minimise any vibration. Set up the flywheel and crank in the block and use a gauge to test run out a couple of cms. down form the edge.
Lightening the flywheel is another matter. It will help speed up gear changes by decreasing the amount of momentum in the system. However not everyone likes the difference. One of the best known US racers insisted he preferred a full weight flywheel as it enabled him to hold onto a certain gear for longer at some circuits.
Personally with a +8 , as David says, the flywheel was designed for a much heavier vehicle, so I am happy to have mine considerably lightened. Again , as per David , John Eales would be happy to advise. He is very familiar with this engine in Morgans.
