I am new to posting here, but I have been reading for a while. I have a 98 scrambler 400 and have recently rebuilt the motor. My mods are an Aaen top end pipe, Boyesen Rad Valve, Aaen trail porting, Aaen head mod, 38 TMX carb, .020 over Wiseco piston, factory box with Uni filter and others that do not pertain to this question. I am running at a 12.5:1 compression ratio. After my rebuild and some upgrades I ran a mixture of 92 pump and Turbo Blue racing gas. Everyhting seems to be running fine, but after lots of research on the internet I have read so many things on what gas to use that I am kind of unsure. I have read that mixing leaded with unleaded was bad for trying to tune in just right and I have also seen racing gas suppliers say that with a Compression comparible to mine I should be running at least a 108 motor octane rating. Does anyone have any thoughts? Thanks

 

Check with Bubba297 or modquad.That is thier department.They both have highly modded 400,s.