A question that often crops up is how to lock crank/flywheel when removing nut on end of crankshaft. Not sure how many are aware of the following, something I learnt recently on a chainsaw maintenance course.
There is a special plastic tool that is inserted through spark plug hole and prevents piston from reaching TDC thereby locking crank. See example here Not sure if this would work on the engines we encounter eg Villiers, B&S, JAP etc.
Various versions of that are available but really only suitable for 2 stroke applications where the spark plug is immediately above the piston. A length of heavy starter cord stuffed into the cylinder through the plug orifice is just as effective and is
“universal” !
I’ve used the string method many a time and never had it fail yet! Another method is to insert a wooden wedge through the exhaust port on a 2-stroke to lock the piston. That way you aren’t putting undue pressure on the threads of the spark plug hole.
If you’re undoing flywheel nuts another tip is to look to see if it has a left hand thread- most are standard right hand, but every so often you come across a left-hooker and you only strip the thread once!
Someone did advise me that if using the string method it is better to use hemp rather than man made fibre as hemp will burn rather than melt should any break off inside combustion chamber.
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