But many street motorcycles have 12:1 compression and run on premium gas e.g 2008 Honda CBR600rr 12.2:1
That’s a different animal; not all compression ratios are the same. That bike is rev’ing to what, 10K RPM? 15K RPM? to produce its horsepower? And I’d wager they have every ounce of weight shaved off of that crotch rocket.
Your torque demands on that engine are slim, at best, and they don’t have the emissions demands placed on that engine that cars do. Let’s ignore the auto emissions issues and the timing games that emissions computers are doing on engines just now.
The bore is 67mm and stroke is 42.5mm. That’s just about backwards from an engine where you want to produce torque; you want smaller bore diameters and longer strokes. Longer extraction strokes are how you get thermal efficiency up in a piston engine. Since they have a hugely “over-square” engine there, I’ll guess that their “three dimensional spark mapping” (whatever that is) is a way of forestalling the last bit of compression as late in the stroke as possible (which is due to the over-square dimensions) and then lighting off the charge in some sequential way.
You can buy a 500 CID Cadillac engine built like that and it weighs only 65 more pounds than a 350 CID Chevy...
We have run the 425 heads on the 500... does just that goes from 10:1 to 12+