To give a graphical understanding of the effect of the balance factor (BF) here are some diagrams:

Staring at TDC the crank rotates clockwise alpha and the rod rotates counterclockwise beta. The BF is opposite the crankpin.

The mass centres move like this:

The piston only moves vertically, the rod centre moves nearly elliptical and the BF moves in a circle.

At 72% BF the radial forces on the crank are these:

The piston stopping at TDC and BDC makes a high radial load. It goes to zero where the rod angle and crank angle are 90 degrees (approximately 72 degrees ATDC).. The BF is a constant radial load away from the crankpin. Note the total radial load is biased on the negative radial side, the BF load overcomes the rod and piston load for most of the revolution.

The forces in the X (horizontal) and Y (vertical) look like this:

Notice the total forces are greater in the horizontal. A rider notices the horizontal vibration less than the vertical.

At 50% BF the radial forces on the crank are these:

The peak total forces have become more equal.

The forces in the X (horizontal) and Y (vertical) look like this:

At 50% BF the peak loads on the cases are lower.

An additional term, not included, is the rotational inertia of the rod as it swings.

Balance weight used here is Rod(BE) + BF * (Rod(LE) + Piston)

However, as John stated, the amount of perceived vibration depends upon the resonance to the frame and other hardware..