I was wondering how Yamaha can sell at least three of their newest bikes off the show room floor running at 11.9 and 12.4 to 1 compression ratio. The YFZ is 11.9 and the R-1/6 is 12.4. All three appear to run off of pump gas. How can they get away with this without running race gas? Do they detune the ignition module or are they magic?

It almost appears we could go to our stock ignition curve and run 91-93 octane pretty safely with a 12.5 to 1 ratio.

jbt

 

my gsx1300 is running 11.0 comp and does fine on pump gas. i run 92octane on the street but run sunoco in it at the track.

 

The Z400 runs a 11.3:1 and in the owners manual they recommend 87 octane. Go figure how they can get away with that.

 

The timing is crazily advanced on the high comp sport bikes.

The plug fires sooner to avoid detonation... I think