Looking at your earlier posts I assume this is for the 150 2 stroke. We have only run 2 stroke KTM's for the last 12 years. We have gone through the grades and are now in seniors. We ride a 150sx. When racing 125sx bikes we did some testing and compared 98 octane pump gas to 110 octane Aviation Fuel (AvGas).
Here is short the differences:
Hope that helps.
- Pump fuel in New Zealand come in 3 octane levels: 91, 95 and 98 octane (we do not use fuel that has ethanol mixed in).
- Before we tested the AvGas we had tried with all three pump ones. 98 worked best as it allowed us to set the motor ignition timing a fraction earlier allowing for more fuel burn and less pre-ignition (Ping-ing).
- We then tested straight AvGas and could set the timing earlier without any Ping-ing. This gave us an advantage in clearly noticeable more bottom end power, and we raced with 110 Octane AvGas for 2 years. Then after some discussion (with other riders and on here) we went to 50/50 98 and AvGas. Reason was that we could then get the best of both worlds: We had led in the fuel, still high octane (close to 105 octane) and we could leave the timing early. As the 98 fuel burns faster than 110 octane we also got some more bang for our buck increasing the explosion. We still have to test with 95 and 91 octane.
- We never did any jet adjustments or anything else for the new mix. Any jet changes always had to do with elevation and temperature on the days we ride.