My very first remembered encounter with these beasts was about 1970, a friend's father asked me to help him cut the B.W's canal towpath from Braunston to Coventry, I had no idea of how long that was or how long it would take, but was unemployed and it sounded like a good idea at the time. We had no long handled fork required for flicking the vast amounts of grass off path (my job) so I had to make a decent rake before the job stat, I went to my local DIY and bought about ten feet of 2X2 pine, I cut about 2' 6ins off one end and drove in five inch nails after having drilled eighth inch holes firstly. I also put in three longish wood screws, one each end of rake part and another in the handle to give it strength, I ran a piece of galvanised wire around the screws to tighten the head end up. The machine was owned by British Waterways and was a four stroke, fairly reliable too, except where the bank had given way and machine went into the canal a few times! A strip down of the carb. generally had her going again in a short while, we once lost the float holding steel pin and only found it again after trimming a yard square area of grass by hand!
My father and brother in the 80's did some gardening for a local Sir and told a good story about another machine that sometimes stayed in gear, the only way to stop it was to aim it at the nearest apple tree!
My next door neighbour was the local allotments assoc. chairman/treasurer and asked me to look at theirs, fault was occasional backfire which sent engine backwards and loosened off flywheel, I did the usual service, air filter, plug, oils, check of points, capacitor etc. to no avail, every time I thought I'd fixed it, it was OK for up to a minute or so, then it would do the same, the next time my finger inadvertently touched the HT lead I got a "belter" as one of my brothers in law calls a nasty shock, yes, the old rubber covered HT lead had tiny cracks in it and was useless, a length of modern car type stuff fixed the machine permanently.
I did some sub contract work for a mower business a mile or so from Milton Keynes, one job was on a Allen Scythe, owner himself told me how this was a real head scratcher as he'd actually stripped it out himself, his workforce being young men didn't really want to work on it. Within minutes I'd found the main fault, he'd only shorted the points and capacitor out permanently! He seemed surprised to hear it barking away so son and wanted to know what I'd done, as I'd used no parts at all, when I told him he wasn't very pleased, he seemed a bit vexed that I was somehow questioning his mechanical abilities, which to me then weren't very high! When I found out I'd only been set on to make another employee make his mind up to leave or stay and he'd almost run out of work for me to do, I left, but that's another story.
Despite their obvious drawbacks of noise, poor manoeuvrability, etc. I do have a sneaking regard for the old things still. Have just remembered that the canal one used a piece of knotted rope to start, not much fun when a 'dunked' engine is having an 'off day'. But with a good flat run and damp grass or weeds, it's amazing just how much stuff you can cut.
I can still recall carrying my home made rake in one hand and the spare cutter bar on my shoulder, with the sharp blades very close to my fingers, friend's dad kept changing his mind about where to have bar, you can mount them centrally or to either side, but you have to move the part that drive part engages with, he used the heads from big nails to do that, five or six inch ones. It was a bodge, but it worked, the correct rivets would need heat to get them fixed correctly I now believe.