Crankshaft Balancing - Build-Off - Greg's Bike

I had just received the polished motor from J&D Polishing and was about to start assembling it when I realized I needed to balance the flywheels first. I started asking about crankshaft balancing, eager to find a capable shop because I know how much balancing reciprocating mass can affect a motor's performance. Plus, this particular motor has an untested mounting system-the existing mounts should be more then adequate, but reducing vibration also reduces fatigue on the metal and the rider.

Eventually, I asked Brian Nallin at Revolution Performance based in Plymouth, Wisconsin, if balancing my crank was something they could do. He replied, "Of course we can, haven't you seen our website?" Then he promptly brought me up to speed on the most advanced crankshaft balancing techniques: dynamic, instead of static, balancing. Dynamic balancing actually balances a crank while it is moving, while factoring in the weight of each piston. Think about how wheels are balanced nowadays, on a machine that spins it at high-RPM to make sure it is spinning with little or no vibration or wobble-the same principle is applied to the flywheels of a V-Twin. Every vibration can be attributed to a loss of power, all vibration is misdirected power-smooth is always better.

I sent my stock 883 Sportster...        read full caption I sent my stock 883 Sportster crank to Revolution Performance; here it is ready for disassembly.	First, Revolution Performance...        read full caption First, Revolution Performance takes the crankshaft assembly apart.	Balancing the crank starts...        read full caption Balancing the crank starts with the pistons. Because I upgraded the cylinders from 883cc to 1250cc, the pistons had to be matched for the new size jugs. These are forged aluminum 1250cc pistons from CP (in stock at Revolution). They come complete with wrist pins and new rings.
Each piston is weighed, and...        read full caption Each piston is weighed, and if necessary, weight is removed in order to get an equal weight between each piston.	Reciprocating mass can get...        read full caption Reciprocating mass can get to speed faster if it weighs less. They machined almost 3 pounds from the total weight of the wheels, meaning it will take less power to move the crankshaft, and reduced parasitic drag.	The removed material is evident...        read full caption The removed material is evident here, instead of 90-degree angle edges, they turned it down to two 45-degree angles.