the higher the octane the longer it burns, making it cooler. I'll give you the full story and then some, hope it helps. 87 burns quicker so if you take the same amount of fuel under compression and burn it and it burns at the same temp, then apply the fact that 87 is quicker then it means more heat at one instance. So if you run 87 oct when it ignites it blows up at the right time and burns all the fuel before it can leave the cylinder and as it is quicker it throws the piston faster. the reason for high octane is that under high compression and/or heat low octane fuels can pre detonate. think of a diesel in runs without spark just compression and heat. Say diesel is 60 octane. What happens in sleds when you put more power to them it raises the rate of compression because its turning faster with more power, and usually raises the rpms a little to. Most mod sleds run a little hotter as well. So with low octane fuel it can blow up before the ignition ignites it and the fuel burns on the compression stroke rather than the exhaust stroke and causes a lose in power. the higher the octane the better it holds up under compresion. When a two stoke(sled) gets a lot of heat under the hood and in the engine it progressively makes it run hotter, so once it starts to increase the heat it keeps going. the air fuel mixture runs through the crank case so if the engine temp increases so does your A/F mixture making it more likely to pre detonate. Let alone the rise in temp of the full induction system, I think we've all seen the melted chit under the hood of a m1000, you know that has to make an effect on intake temps. the sled has a air intake temp sensor to keep this kind of thing from happening but some don't have det sensors and the air temp increases a lot as it enters the crank case.
