Ways to tell if a used damper is past its "sell by" date:
The damper’s rubber ring will naturally decay with age, mileage, exposure to hot chemicals, vibration, ozone, and ultra-violet light, and become unsuitable for even a stock engine.
Visible signs of damage and potential failure include:
the rubber is partially missing
the rubber is discolored gray or “chalky”
the rubber has surface cracking
the rubber has been partially extruded
the damper rim is dented or bent
If you can rotate the outer rim on its hub more than a few degrees with a strap wrench &c., it’s gone.
If the ID is galled, or the opening is bell-mouthed it may be stretched and won't be a tight fit on your crank nose.
