Isn't the garage capable of listing HP of the bikes? I haven't looked in a while, but I think the Hyabusa has the most HP in the list.
Regarding the 8H bikes...
The Suzuka 8H bikes are moreso created from factory-stock equipment than even the SuperSport/Superstock bikes, or "RM" models in the game, which only have to keep the frame, cylinder, cylinder head, engine cases, transmission case... and I think that's about it. In respect to actual racing bikes, the factory "RM's" will make more power and in a less-usable range than an endurance bike will.
In real racing... at least AMA Racing, the classes are as follows:
Superbike - 4 strokes, 901-1000cc, custom frames (Like the Honda RC51). We don't have Superbikes in the game that I can think of.
SuperSport - 0-600cc 4 strokes, production machinery (The RM of regular 600cc crotch rockets)
SuperStock - 745-1000cc 4 strokes, production machinery
Formula Xtreme - Production 4 strokes, mix of twins and 4-bangers and liquid or air cooled, with accompanying displacement classes per disadvantage of motor design.
Thus, it is my contention that the endurance bikes don't even have the high horsepower of the Supersport or Superstock bikes (RM) that the game gives you. Any of you following racing will also know that privateer efforts often don't have the R&D money to compete with the big Factories, though their racing program is often as successful, if not moreso. But that's not the point... Money is usually a limiting factor, as is testing time and data, and you'll often find that the factories will "spank" the privateers MOST of the time with bikes outperforming them on the dyno. Again, this is not to say that privateers cannot develop a more powerful machine or race successfully against the factories, but speed costs in racing - and the factories have the $$$ to spend. If the game wishes to be accurate and not cowtoe to (wonderful) aftermarket companies, it would list the horsepower as something surprisingly lower than you'd think on an 8H bike.
Lastly, you can only go 100% for X many hours on the bike's lifespan. A typical AMA race is 100km... or about 10-20 laps... not even an hour... all depending on the track. Now multiply that lifespan by 8 hours, and realize that you're taking too much "life" away from the engine (X hours, remember?) - to compensate, and make the bike last the full 8 hours, you need to tune it down a bit. A bike will last exponentially longer at only 95% potential, and give you X+Y hours. Make sense?

Maybe not?
Either way, it's my belief that an endurance bike, and a privateer one at that, will have lower horsepower than the factory RM bikes. (LOL - even though I use the 7Honda or Moriwaki!!)
