I'm only running 40mph Butre, but have over 1000 kms on this engine with only one "pedal home".
After hours and hours of crazy rpm, a piece of wristpin circlip broke off, scoring cylinder and piston.
I find these motors very reliable and wonderfully easy to hotrod and repair, better than much of the production machinery I worked on over the years.
As for need for huge octane, I've learned to get by without it.
I got my license in the 1970s when they stopped selling high octane gas here.
1960s supercars were selling cheap cuz they couldn't run on the only available low octane fuel. I bought a rusty 1970 11:1 351Cleveland "Q"code Torino for $120 and using lessons learned from Ak Miller, Larry Widmer and others writing at the time, made it breath fire on low octane fuel. This is that motor stuffed into a Ford Maverick (on 83 octane fuel):
I had a CR250 that needed the same work. Today I have a KTM 125 EXC that I take on long wilderness excursions. In the back-country a lot of general stores only have 83 octane so my 125 is tuned to run on it. I am typically always the smallest bike and yet I run in the front. Don't need no 90+ octane to get a KTM 125 to run 140 kph and keep up with the DRZ400s. I cannot out accelerate the 250 2 strokes, but I can pass them on the long stretches with a higher top speed.
My point is, power can easily be built out of regular fuel.
Most amateur "High Octane Motors" I've seen didn't gain anything from the fuel, but used it as a crutch for a poor build. My potential gain for building an engine to use 95 octane instead of 83 is less than 8% more power. Why would I ever go to $$$ 100+ stuff unless I was racing professionally?
My little 66cc Grubee could power my heavy arse up the steepest hill in this county faster than I could ever pedal on the flat, all on (slightly modified) stock parts and 83 octane. Not even a tuned pipe. What could I gain if I built it for more octane? Not much. Just not as fun to ride because fuel would be a pain.
To double the hp of these motors is not that hard or expensive. They are reliable if you know your stuff and build to avoid detonation and vibration problems. No special tricks needed.
Steve