Ok....I put it on in the fashion shown, wasn't easy at all due to the previous owner having cut or altered the cable that moves the tension pulley.
Alas in doing this adjustment I think I've caused another issue. I had the mower tilted over heavily on its side - not 100% over but well most of the way. I was sure to tilt so the carb was upright and had no fuel in it.
But when I fueled it to try the new belt alignment I got it spluttering to life with a LOT of smoke. No big deal I figured a lil oil went in the cylinder, it'll idle it off.
Restarted and it surges initially and then immediately cuts out.....tried restarting and even with throttle adjustment it quickly cuts out, but not any white smoke anymore. Allowed it to rest overnight, not won't start at all.
Has fresh fuel, checked plug, removed airfilter cover and tried. Nothing seems to work. I've not altered anything else with it so dunno what the possible issue is.
Stumped for now.