I met up with quite a few of these old 'clonkers' in my 30 odd years of repairs etc. various different engines were used, but it appeared that I would only encounter the sometimes finicky Aspera engined versions or maybe worse, at least when not running right, the eternal Briggs. I almost took the poor starting Aspera engined model I'd bought on a part exchange on to a local cricket club to sell, but at the last minute decided another carb. clean out would help, good job I did, the bottom carb. anchor screw was hollow and about half way up was the tiniest little hole imaginable, I believe it was the feed to the slow running circuit, the difference was amazing and the club rep. was very happy wih it.
Often owners would quibble at the price of genuine spares, the two dry cotton belts were double that of unsuitable 'off the shelf' type replacements, sheaves of the pulleys were of a different angle too, I believe.
As recently as three years ago I tried to help an old chap out who'd bought a machine from his neighbour, who was a self styled 'fix anything' type, ordinary black rubber belts with the wrong profile were fitted, just for starters. I fitted the correct belts but only adjusted the bottom blade, customer was being 'guided' by the man who'd sold him the machine and 'serviced' it, it turned out. Machine had a seat with roller, grass was damp and I got called out again after machine failed to pull itself and owner around some tight bends around flower beds etc. Fault was due to ratchets in rollers having failed. I stripped the machine out and was dismayed to find only one ratchet spring still in one piece, rust and soil etc partly filled each side. I could only give the owner a fairly large estimate for the new parts (if I could have found them or made new) plus fitting, he was very upset at the time due to the HS2 having been newly announced to run within close proximity of his property vastly devaluing it etc. he told me to put he old belts back on and bring the machine back, I was expecting to not being paid, but managed to break even with him, I felt very sorry about his HS2 problem, but I was a mower business, nothing to do with anything else, I don't think he believed my diagnosis!
Anther machine I cleaned up well, had cylinder sharpened and I serviced it too, within weeks a man told me his 'boss' was very interested in it and would like a trial cut in his large garden. I asked what sort of machines were used already and was told a ride on and a large walk behind rotary. I instantly knew I had trouble, I tried to explain how a lawn that's been cut by rotary machines, even closely, will not be level enough, nor low enough for a cylinder to tackle, without a lot of hard work. Against my better judgement, I took the machine out one dry evening after work, took tools too! 'Boss' was a young mid twenties yuppie type who knew nothing about grass or mowers, my two years as a greenkeeper and grass type advice fell on deaf ears. The mower was cutting paper like scissors all the way along, but the amount of grass was ridiculous, I measured it at two inches, but machine was set for about a half inch, I adjusted it to 1.5 inches the highest cut available, but going was very hard, belt was starting to slip and almost full throttle had to be used, grass was like mustard and cress! Box was filled in a few yards, there was just too much grass there, I tried to explain to the pair, but they looked at me as if I'd come from another planet!
Boss kept looking and saying nothing much as if things would suddenly change, I repeated to him that there was too much grass and that you can't simply jump from one type of machine to another totally different way of cutting, "tell me why again?" he replied. I was very hungry and ready for my tea, boss came up to me and said his gardener would help me back onto my truck with the Webb, asking about payment for my time and trouble he just walked off! There are rude and ignorant folk about, what they don't understand doesn't seem to interest them at all. The lawn was at fault, not the mower.
I still have a towing hitch for one if anyone wants to buy it.