We did have one Foden mixer with a 'stroker fitted at our quarry for a while but apart from changing some filters on it we did no other maintenance as the mixers usually went to Stafford for repairs etc. The lad who drove it had a hand with hardly any fingers on it, an abnormallity from birth, but he could make it sing! I have seen a pic of the original single cylinder engine and it was interesting, I can’t remember whether it was in Foden’s museum when we visited in 1976? The last firm I worked for had run an ex Sellers and Kent Foden eight wheeler flat many years before and that had the two stroke fitted. I remember the senior partner (the late Frank Gough) telling me that he rode from Wirksworth up to Manchester one saturday alongside the regular driver as there was an urgent load of asphalt blocks to be delivered and he had never seen a man change gear so rapidly before in his life! "We passed every lorry and quite a few cars up those banks between Newhaven and Whaley Bridge " I remember Frank telling me “and it wasn’t bad on fuel as well”. When I worked for them they still had the parts book and workshop manual for it, plus some other books on Dodge trucks etc, and he offered them to me when the firm closed down as he knew I collected Foden memorabilia etc and would have liked to add it to my collection. We did a deal but when I asked him about calling for it somebody had offered him more money so they got it alas. 
I think the two stroke was a brave attempt by Foden’s to try something in heavier weight trucks that British operators were not used to, and even to this day they have never really accepted anything other than ‘traditional’ four stroke engines.
Pete.