Hutch wrote on 12/31/69 at 16:00:02:Not really sure when they started calling them S-40, and that's when they lost top end or not. Sorry, what I meant buy all being different was that one site says, the hp for say a 96 is one thing and another says something else. I can't even find a site with hp and rpm stats for an 04-07 S-40.
Honestly, I don't think there have been any internal engine changes. I've been reading this same subject since about 2001 (when I first started online). Everyone has wondered about the HP and a few have done dyno runs. Everyone has tried top end speeds and 1 or 2 have made it over 100 with some mods.
I think that HP is possibly mentioned in the MOM, but I'm not sure where mine is. 30-31 HP at 6,000? I don't know. I do know that mine turns an even 3500 at 50 mph in 5th, so by doing the math that really tops the bike at 85.
With the exception of going from 4 speed to 5 speed and some jetting changes (excluding California models) there has been almost none...except for changing the name, too.
There are a couple topics in the tech section about changes and the carb specs, but I don't know how well they've been updated.