Originally Posted by mrslappy 
Crankshaft balance is very important at high RPM. Thus why many manufacturers will use a 4cw crank for motors that are not reving as high. This is to lessen the load on the engine and thus it takes less power to keep it running so you get more power to the wheels. At higher RPM the 8CW crank is heavier but is more balanced for longevity. Ideally the Reciprocating weight of the Rod is balanced out by the counter weights. I always go for the lightest possible parts in the engine. In a 4 cylinder motor, I do not try to keep the amount I take off the crank the same as the rods and pistons. I will get the rods, pistons, piston pins, rings, bearings all done and balanced out. Then weigh the rotating and reciprocating weight. Then get the crankshaft as light as needed and knife edged. Having a heavier crankshaft with lighter rods and pistons will be more balanced and high RPM stability and longevity than a super light, wimpy crank with very strong, heavy, rods and pistons. Getting the crank knife edged and cut down for windage will be more beneficial than a super light crank with poor windage characteristics.
Of course most of this is out of most peoples pockets but if you do a few of the right things here and there, its definitely going to show on the dyno and in smoothness.
-Ted
That was pretty much what i had thought as it seemed logical to me to remove the same amount.
I completely agree what you say about lightening and windage.
The first motor i ever built was a mini motor and i spent a lot of time lightening the crank rods and new cast pistons (new cast pistons because i was only 17 and thats all i could afford) I then had the whole lot balanced to 10k including flywheel clutch etc and that motor was one of the smoothest fastest revving motors i've ever driven.
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