Thanks for that Garthh. You've made explicit what was perhaps implicit.Turning backwards can make the cam chain jump on some motors,
I don't know that this is the case on burgmans
These engines have got chain tensioners which could potentially create a problem if turned backwards but as you say unless somebody has actually had a problem then it probably doesn't exist given that the manual doesn't mention it. Perhaps it's more of a case that it's probably better form to always turn forward.