thats OK Doc.... i look forward to your whining when someone shows up with an RC4 and races in ULSB and whoops everyones ass.
Printable View
The Duc runs C12... :D
Not really a good comparison. Air cooled Duc's need the C12 if the compression is increased much above stock. Not as efficient and or uniform cooling plus combustion chamber design cause the need for the increased octane requirement of C12 for the Duc's.
I am not familiar with the Hawk's but they are water cooled which helps alot with alleviating the need for an increase in octane. Of course all combustion/induction modifications can affect this.
Bottom line is that a well designed combustion chamber will not require as high of an octane requirement as a poorer design. That said you want to use the lowest octane fuel that will NOT cause pre-detonation.
:beer:
ps - I'm glad that it appears ULSB will still be a Hawk competitive class at LRRS. I think the Hawks are cool bikes and the fact that after 2 decades they are still competitive says volumes!
good info in there. thx. how does one tell if they have pre-detonation?
Pre-ignition is when the intake charge is ignited too early. The combustion pressure exerts large forces on the upward traveling piston and can destroy the engine. On the other hand, detonation can occur at any point during the combustion process. It is basically a violent and uncontrolled explosion in the combustion chamber. Although folks commonly refer to combustion as an "explosion" it is actually more appropriately termed a "controlled burn". Explosions in the combustion chamber are undesirable, and the violent release of energy can also destroy an engine. Pre-ignition can sometimes lead to detonation because the premature burn is simultaneously compressed. Pre-ignition and detonation are both bad news. Detonation is usually caused by a *lean* A/F mix. (Vacuum leaks) or improper jetting. Also by low octane fuel,over advanced timing, lugging of engine, and of course excessive carbon in the combustion chamber. A rich mixture can lead to detonation due to excessive carbon buildup in the combustion chamber decreasing its volume and raising the compression excessively.
Listen for pinging. :D
If you're not sure what pinging sounds like, imagine dragging a screwdriver across the fins on an HD very fast.