Sometimes taking the head off will allow the barrels to loosen from the base , causing a leak at the cylinder base . If the barrels are coming off then rings are a good idea . If you can't measure the bores yourself then get someone to do it for you . They need to be checked for oval , taper , and to be sure they are within spec for diameter before a decision is made to hone and re ring . Bores that are right at the limit may end up over limit by the time the new rings wear into the newly honed cylinders . While its apart consider replacing the cam chain ,and all the rubber bits ( rubber tensioner pins , rollers ,and slider ) . These pieces harden with use and age and can shed bits which will end up in the sump . The hard rubber also makes things a bit noisier . There's also the primary chain tensioner (rubber roller ) but you need to split the cases to get at it . I don't know about you but I always end up spending way more than I intended when I take things apart . Oh , I almost forgot the head (check valves , guides , seals and seats ) , maybe do a little port cleanup .
