Which Ratio For 440 Big Bore Kit

[keith mcdonald]

I am considering a Wiesco big bore kit for the 400 in my sig.They come in 2 comression ratios 11to1 and 12.5to1.I am planning to race open class C moto in spring but I still like to trail ride.What fuel does the 12.5to1 require.I currently use 94 octane with a heathy dose of octane booster to prevent detonation.Any advic will be apreciated.

[cals400ex]

stay away from the octane boosters. they can actually do more damage than they help. with 12.5:1, you will definately need straight race fuel. on the 11:1, you can probably get away with 94. some prefer to mix it with race fuel. i have tried both on my 11:1 and it isn't quicker either way. it runs the same, even after a few hours of riding.

[keith mcdonald]

How much horse power do i actually stand to gain with a big bore kit with either ratio?My bike runs pretty darn awsome now.Should I expect a 10% improvment to go with the 10% displacment. Were does the extra power come in bottom ,mid ,or top end.I would appreciate any info before I decide on whichif any kit to buy.

[frogburner]

I run a 12.5:1 and I do not have to run race fuel if I keep air across the motor, I will run race fuel if I am going to be in the woods though. I found that octane booster is a joke, if you read the label closely, it only raises your octane by 1. Octane booster raises fuel 10 points, which, 1 point is equivalent to .1 octane. So do the math, 10 points=1 octane. If you do run a 12.5:1, you may want to beef up your head studs. My 440 has gobs of power, and when I use my higher rev box, it really runs good, but I only use it when I am drag racing..