it's definately a honda motor, i've been riding rgv's for years and know all about aprilia using the vj22 etc. the guy apparently has lights on it??? i assume from what you said that the rs250 doesn't run a magneto or anything like that. could he have fitted one from an nsr? the bike is apparently making 82hp at the wheel if that helps with the year. can the motor be jetted for more mid range?