Unless your engine has an unusually high compression ratio I don't think increasing the octane is the answer as increased octane actually slows combustion . Unless the engine mfg requires high octane using 87 to 89 is best as long as it is methanol free and it's fresh . Fuel age is the biggest issue to impacts volatility . There are several good videos out there on setting the timing using a protractor to indicate TDC Set the timing to 28 to 30 BTDC the spark should occur within that range. The slight free play feeling at TDC is normal and on these engines does not seriously impact the ability to get timing set within the proper range . 2 or 3 degrees either way is not an engine killer .