KX500 Why you should balance your crankshaft

[Sandblaster]

The following is taken from a post from Tom Morgan over on Facebook.
It follows very closely to our opinion as well...

Tom Morgan Racing: The correct balance is dependent upon the piston and rod weight. On KX500's there are considerable differences in the wights of available pistons and rods which require as much as a 40 gram variance in proper crankshaft balance.(40 grams at high RPM is a noticeable vibration) The balance percentage generally falls into a narrow range but it is much more important to calculate the actual X-Y forces caused by the imbalance. Then I can determine the crankshaft counterweight amount and the location of it that is going to produce the least amount of imbalance and result in the least possible amount of vibration feeling. That being said.....the older KX500 cranks tend to be "over balanced" and the newer cranks tend to be "under balanced". The rod and piston weights have a very large effect on crank balance so if you are changing to an aftermarket rod or piston without re-balancing the crankshaft you will most definitely have more shaking and vibration. This out of balance situation is what causes the main bearings to wear and become loose in the crankcases and on the crank journals. In the decades that I have been building engines, I have never seen a balanced crank have a repeat problem with loose bearings.

In the final analysis, get those cranks balanced...
I send mine to Tom and have been thoroughly happy with his work..