update: Had a look today, and yep, Max was right, broken flywheel key. I removed the blade boss too, key is ok, but looks like the bar-blade and blade-boss have a dent in them. Took out a hammer to straighten a bit, but might have to look for a spare just in case.
(see attached pictures)
Had a quick look for the key, seem a bit pricey compared to B&S flywheels. I'll have to work out what model Honda this is a clone of and maybe search for that.
While I'm here, a spring came off the base of the mower (see pic). Anyone know what it's suppose to clip to ?
