The 397 is going to be grossly exaggerated.
I'm glad our world-recognized authority weighed-in on this. I think you could swap-out the first digit '3' for a '1' and still be optimistic. That would make it 197 RWHP which is almost 100 HP above your stock engine's RWHP which should be about 110. The factory 145 HP for the USA models is an 'at the crankshaft' reading. From reading all the bike magazines over the years, the highest RWHP reading I recall is 119 RWHP. The factories are known to assemble from 'best tolerances', bikes which are provided to the motorcycling press for testing. Also, another practice manufacturers use is to give the first year's bike a 'hot' set of cams to generate an impressive HP # for the magazines (now, the internet) to 'ooh' and to 'ahh' over. Yamaha did just that with the same-period FZR1000 'Genesis' engine, 5 valves/cylinder. The first year, it exceeded the VMax RWHP by a bit, but then, It weighed 100 lbs less, and had much-better aerodynamics, so of course its top-end was impressive for the day. It made 122 RWHP. That was in 1987, but for the 1988 model, they put in a set of cams which produced much-less RWHP but which had a much-stronger midrange. That made it a better ride, as that's where you do most of your street-riding.
