Hello all. I have a race engine CRF450 that I have spend thousands in race fuel to deal with the high compression ratios. To start, I have a CRF450 with a 101mm cylinder @ 14:1 and I need a fuel that can handle it. I have tried to run premium with high overlap cams and its anti-knock ability is not cutting it. From what I have read and tested, E85 will make more power than gasoline. It has the ability to rapidly cool the intake charge when it changes from a liquid to a gas. This increases the density of air in the mix and increases power. How much power? I do not have any tests, but I would say it is on par with U4.4. There is a high boost in power at the bottom end and a slightly flatter top end. I am told if a 50/50 mix is used a system purge is not needed after riding. As a precaution, I drain the tank after riding and pour in some 93. Then I start the bike and wait for the idle to drop and keep it running by raising the throttle for about 2 minutes. Then shut it down. The idea is to keep the E85 in the carb to get it started, then when the 93 comes into the carb it will richen up to a point it won't want to run. This burns all the ethanol out and leaves it with gasoline. Before I ride the next time I drain the float bowl, drain the small amount of fuel I poured in, fill it and ride. For the FCR41mm you will need: N427-OC FBH/017-384 needle set on the bottom clip 53pilot jet and 220 main jet. I add 1oz of Maxima 927 oil to each gallon as a top end lube or find some premix that is bean based so it will mix with the alcohol. Pure castor can be used but does not burn as clean. It is highly advisable to get an O2 sensor and jet WOT for 12.7:1 with the O2 meter calibrated for gasoline. Idle mixture will be about 12.4:1 I have also read that E50 up to E100 does not make any additional power. So.. if you can get away with E50 @ 101 octane use it. However, I do not know the changes in fuel needed based on a 50/50 mix. Advantages of running E50 over E85: more lubrication and less jetting changes. O2 jetting calculator for any fuel blend: http://www.hotrod.com/articles/wideband-oxygen-sensor/ Octane calculator: ((fuel 1 % X fuel 1 octane)+(fuel 2 % X fuel 2 octane))/100 Jetting increase: multiply current jet size by 1.35 main jet pilot jet: multiply current jet size by 1.5. optimum pilot jet size is when highest idle is at 1.5-2 turns out. Fuel injection bikes cannot be changed unless the system can handle the ethanol and has the injectors changed for the added fuel as well as fuel demand increased(fuel pump and mapping). The results I have here are for my setup and may only be a starting point for others. As a comparison: I have another carburetor that is 43.5mm and I needed to hand sand the above needle to get the 1/4 throttle position richer. I did not try and use additional shims under the clip, but it may have worked.