If your 650 engine no is between DU44394 and DU887147 then you can reduce running temperature and therefore extend engine life at no cost, next time you have the crankcases apart. From DU44394 an oil pump with better scavenge capability was introduced and after DU887147 the crankcase oil level was increased by shortening the length of the scavenge pipe. All you have to do is shorten your scavenge pipe by cutting 5/8” off the end. If your motor is pre DU44394, and you have fitted the later model pump the same modification obviously applies. I made this modification to my 62 Thunderbird and didn’t notice any difference. I sold the bike (bugger) soon after so don’t know whether it improved wear.