dont mean to pi55 on your bonfire BUT, your better off using a lower octane fuel (no more than 97ron)
as the fuel just ends up burning in the exhaust rather than the cylinder. something to do with ignition and port timing i believe?

just a quick comment, the shorter and fatter a pipe, the more torquey the motor performs. the longer and thinner the more top end you tend to gain. i'm no expert on either of these subjects but i'm sure someone on here is just about to put me right

regards,
paul.