Well I post this to assist others.....in lieu of any responses or suggestions I found through trial and error that it is likely a M36. I had bought a M37 as stated on the ODK store but that was far too loose. When engaged I got no movement whatsoever. I tried an oldish M36 I happened to have onhand and that worked well. So being that the belt is tensioned by a pulley pushing in from the rear I don't think straight rubber belts will last very well at all - info says to ensure that they're wrapped or better still kevlar. So ordered one of the latter.
I have to say when it's working well it's an incredibly formidable and brutish mower......I don't know if the carb could do with having the poppit(?) adjusted but it revs very hard and really moves at a cracking pace when the SP is engaged. Only the thickest sections of kikuyu slow it down at all but the motor shows no sign of being stopped by this.
Really great design by Victa.....if and when i tire of the 2-strokes on them I think they'd definitely be wonderful to splash a bit of cash and put a top quality 4 stroke motor on them - something like the B&S 850. But will hang in with the 2-strokes for the moment, they're pretty tireless and apart from an amazingly high noise level (thank goodness for quality ear covers) they work very well indeed.
