Just a quick note on balancing a Lister, or any low RPM engine for that matter. This works on high revving stuff as well but you need to put a lot more care into making it. A ring of 3/4 tubing is made to fit nicely up inside the rim of each flywheel, around the circumference. Before neatly butt welding it together, inside place 6 to 8 steel balls, and a little oil. Weld it at the top so the oil and balls sit away at the bottom and so dont get hot and burn. For low revving engines, copper tubing is fine and can be silfossed...( hard soldered) together, making sure the balls can negotiate the join.
8 to 10 tabs are also welded to each ring... these are bent around the flywheel rim to hold the ring in position. A note here,,,, once rotating, there is no great force on this ring, as it tends to expand out toward the inside rim of the flywheel, the tabs are simply to hold it in place..
How does this work? Once rotating, the balls will move around inside the ring and automatically take up a position that cancels the vibration. If the weight of the balls exceed the weight required, they will simply relocate themselves to a position that will cancel the excess. This is a form of dynamic balance that changes with RPMs. Both flywheels need to be done this way to prevent "walking".
The effectiveness of this approach can be simply demonstrated by placing a handful of small glass or steel marbles inside a known out of balance tubeless car tyre/rim assembly, refitting to a front axle, and driving down the road. This simple demo wont completely cancel perfectly every time because the marbles are not restrained latterally/axially, but can travel side to side, but will give a very good indication of effectiveness.
Another beneficial effect with this, it also has a small effect on torsional vibration, this is the "twisting" motion, exaggerated by having very heavy flywheels, and few power strokes.
This manufacturing method works well on spoked flywheels as mine are, I cannot comment on the full cheeked versions. Higher revving engines need to use smaller diameter steel "bundy" tube, with more balls, and a more robust mounting method. The effect of this "mod" can be quite dramatic, as any static balancing can never cancel all the forces involved. Depending on the extra weights required, more or less balls may be needed, but err on the heavy side.... varies with engine.