Seadoo Snipe and Rookie that was a damn good thread... I would have to agree though the stock compression on the 2 stroke or four stroke would choose what gas rating the manufacturer would put in the manual. As soon as that compression is changed then a cleaner fuel would have to be run in order for it to properly compress ignite and burn with out the pinging and knock and detonation, again four stroke tech but only for example. I build race motors mainly quads but for bikes as well. My first that I built which is still running was a suzuki ltz 400 raised the compression to 14.8 to 1 from say 11.5 to 1 which the manual called for 91 octane, I beleive, at that compression if I had tried to run 91 octane it wouldn't have started. I ended up having to run 118 octane and certainly not avgas which has a much different density and the carbs wouldn't work right. Of course we are talking about major engine modification head port and polish everything flow matched. but in the case of a 951 which has aftermarket domes that would in effect raise compression, a higher octane fuel would have to be run. Of course its not just that simple but thats what I have been taught and what I have learned, sometimes the hard way:reddevil: I would not recomend running anything hotter than 91 octane in a stock machine though vp and some of the other race fuels out there do offer a fuel for the lower comps. and basicly it burns cleaner and the motor is cleaner because of the additives it is not necessarily a higher octane take vp's u4 I would run that in a stock machine it wont do much in the way of performance, unless it is airrated, but it will keep the internals of the motor cleaner and well it smells real good!!:cheers:
