Logically speaking, used dirt bikes that are not well-maintained would require an inflated amount of repair cost as well as imposing certain level of risk and danger to you.
If you happen to get the trade done with a dealer then chances are the bike would have been thoroughly examined by a professional so basically there should not be any severe mechanical predicaments.
Besides, it is common that the dealer will provide a short guarantee term for buyers.
But anything good does not always appear good.
Buying a used dirt bike from a dealer would cost you much more than buying a private owner.
If you are willing to take the risk to save on your pocket then possibly, you should first perform the examination of the bike yourself.
You can check on the wheel bearings by putting the bike on a frame then spin the wheels.
If they are spinning noiselessly and straightly, then there are no defects.
Also try to pull them back and forth to see if there is any wiggle.
Besides, you can also test drive the used dirt bikes to check if the gears are functioning well.
Beware of strange noises and take note that the brakes should not be grind or mushy.
A test ride would reveal if the bike's shocks and suspension are working well.
However, be cautious if the bike has undergone modifications.
More often, modifications are done due to the over ridden of the bike so think twice.
Apart from making evaluations of the bike, you can also observe and interrogate the owner when you are buying a used dirt bike.
You can question the owner or dealer regarding the used bike and if he shows signs of uncertainties such as not being aware about the timely oil or air filter change then maintenance was not prioritized during his use.
Owners who provide proof of more printed documentations are more trustworthy than the otherwise.
They may include proof of ownership, maintenance records and roadworthiness certificate.
These are vital as evidence that the bike is indeed legitimate.