What Octane do you recommend

[Hap Call]

As I understood it, the theory of compression and octane is roughly point of compression vs octane number. Loosely said, 10 to 1 compression would run 100 octane, 11 to 1 run 110, 9 to 1 is ok for 90 octane, etc. The higher the octane , the slower (so to speak) the burn, preventing pre-ignition and so on . Whereas high octane on a lower compression engine may in theory give less power because the burn is slower.

Many stock bikes built today are running 12:1 or greater compression ratios. Octane depends on many factors, such as compression, plug heat range, ignition timing, cam timing, and piston/combustion chamber design to name a few. Corresponding octane to compression might have been accurate back in the '70s but with the introduction of new cylinder head designs (our TSCC heads actually led the way in this area) in the early 80's changed the rules.

You are correct in saying that you could actually lose power going with a high-octane gas in a low compression engine. High-octane gas has lower BTU output per volume compared to low octane gas.

Hap

[Anonymous]

As I understood it, the theory of compression and octane is roughly point of compression vs octane number. Loosely said, 10 to 1 compression would run 100 octane, 11 to 1 run 110, 9 to 1 is ok for 90 octane, etc. The higher the octane , the slower (so to speak) the burn, preventing pre-ignition and so on . Whereas high octane on a lower compression engine may in theory give less power because the burn is slower.

Many stock bikes built today are running 12:1 or greater compression ratios. Octane depends on many factors, such as compression, plug heat range, ignition timing, cam timing, and piston/combustion chamber design to name a few. Corresponding octane to compression might have been accurate back in the '70s but with the introduction of new cylinder head designs (our TSCC heads actually led the way in this area) in the early 80's changed the rules.

You are correct in saying that you could actually lose power going with a high-octane gas in a low compression engine. High-octane gas has lower BTU output per volume compared to low octane gas.

Hap

So I have learned a bit over the years(so I'm not crazy... totally ), and yes I did'nt factor in the other variables required, Chamber design, ignition advance ,etc. Kinda neat how technology has made up for old school knowhow. Sure wouldn't mind sitting over a beer or 2 and shooting the breeze with ya; nice to learn from others.

[focus frenzy]

Any overbore keeping the stock headgasket and same piston configuration will see an increase in the compression ratio...thus the need for higher octane. Now about that pesky shaft drive...

Hap

I am not sure about the head gasket, the one that was on it was a fiber with fire rings type, and the one that came from suzuki with the new pistons was/is a laminated steel gasket without fire rings, I was woried it wouldnt seal but it is holding fine.