Because plate compactors are expensive, many independent contractors try to save capital by purchasing used units from equipment rental yards. This is a massive gamble. Rental equipment is subjected to staggering levels of abuse by homeowners who don't understand the machinery. If you are evaluating a used gasoline or diesel plate compactor, you need to know exactly what to look for to avoid buying a money pit.
I always start with the base plate itself. The bottom of the steel plate should be relatively flat. If it is "cupped" or heavily bowed inward in the center, it means the machine has been run extensively on hard, unyielding surfaces like cured concrete or massive boulders, which warps the steel. A warped plate will never achieve a flat grade again. Next, I inspect the rubber shock mounts connecting the engine deck to the base. If the rubber is severely cracked, dry-rotted, or completely sheared in half, the engine has been taking the full force of the vibration, which usually means the internal engine components are heavily fatigued.
Finally, I do a cold pull on the engine recoil to check compression. If the rope pulls out with almost zero resistance, the piston rings are fried from ingesting dust. I also pull the plastic belt guard off and look at the V-belt pulleys. If the grooves in the metal pulleys are worn deep and sharp, the machine has thousands of hours of hard use. Buying used iron requires a cynical eye; you have to assume the machine was neglected and look for the physical evidence of that abuse.
