Using what you've got to achieve the end of getting the fan off without damage is more important than metric vs imperial. This is the 2020s. Time for the old boy to embrace today's reality. Even in steadfastly imperial America, metric nuts and bolts are an everyday reality there. This is fine (not the threads haha).
Tyler will relate to opting for the shed made foam donut option.
As NormK says, will outlast any of us if taken care of.
So long as the European legalities don't interfere regards two strokes. Let's hope not because the cleaner four strokes have been going backwards for decades.
