even if you run a street bike hard all day long, it's still less torture than a 20 minute race.
think of pulling in the clutch while your engine's still revving at 9000+ in every corner, slipping the clutch to keep the power up, and doing this non stop for ten laps.
in a race, the engine never gets a chance to relax.
on a long trip at wot, the engine is still getting a lot of air to cool it down, and will usually continue to run properly. and it's at a constant rate.
now imagine riding that same trip and grabbing the clutch every 20 seconds and letting the engine rev to the max without being under load, then dumping that clutch so your engine has to grab at full rpms over and over.
the only thing worse would be sitting in your driveway with the clutch pulled in, revving till your engine explodes.
unless you've actually beat your bike to death on the track, it's tough to realize how much more stress racing has on an engine.
and it happens to every hardcore racer out there. even the best built engines will fail. mine, arrow's, venice, ccc, we've all destroyed them.
but on the street, as an example, i had a bike crack the case when the chain broke and whipped around the day before the big "born free" mc show that was held in belmont shores, ca that year.
i had a fully built, brand new motor i was saving for my next race bike so i put that in and rode 35 miles each way down pch to the show and back, all at full throttle on opti 2. no probs whatsoever.
pch (pacific coast highway) runs along the ocean, has a huge bike lane, and most areas near me, the stoplights are a mile apart. so the bike ran for miles without even slowing down.
this was my 24" colson cruiser with a28t on it and would hit 55. i even rode in traffic with "real" motorcycles, getting thumbs ups all the way.
that engine lasted on that bike till i flipped over the bars and took it apart. it's in my garage now and ready for another bike. if i ever build one. i think i rode it at least two years, every day, as it was my main transpo.
plus, it was the last of the grubee starfires. the best engines ever made.
wait... what were we talking about?...