Re: Rotational play in flywheel, cause for concern?
As the piston 'dwells' at TDC you may seem to 'feel' rotational play at the flywheel. This alone is not a reason to condemn a motor but may be cause for further inspection/measurement to satisfy your concerns.
Ideally, you can measure piston travel to calculate any bearing wear. Remove all the spark plugs to make it easier to turn the motor by hand. Starting with #1 turn the motor until the piston 'just passes TDC and started to travel downward, stop and rig a dial indicator with a probe to the piston. Zero the gauge. Carefully reach alongside the probe with a blunt tool, such as a 1/4 drive extension and gently 'push' on the piston while watching the dial indicator to see exactly/any measurement of movement before the crank is moved. This will be the combined bearing free-play of both the rod bearings.
You may have to repeat the test as it can be difficult to gauge piston movement until contact with the crank.
Repeat on each cyl.
