It wasn't long ago that buying a used bike was very dicey. For one, so many improvements came each year that a year-old bike was technically obsolete; even worse was the bike would most likely be worn out because of the quality of production and materials. But since the mid-1990s, suspension development has settled on around 12 inches of travel, engines all have become water-cooled and disc brakes are standard equipment. More important, though, the quality of production, fit and finish, durability and overall reliability of off-road motorcycles have come to a level at which buying a used machine can be a competitive and cost-effective way to obtain a well-performing bike.Yet people in general, and men in particular, tend to judge things by how they look (duh), assuming that if a bike looks good, it must be a good ride. Consequently, the motorcycle business has become very skilled at prettying up used machinery. A new fender, a fancy graphics kit, PJ-1/VHT touch-up paint and some silicone polish can make almost any bike appear well-kept. Off-road motorcycles are unique products for how much abuse they must endure, especially considering how often they are washed. As a result of hitting deep mud holes and being hit by 2000-psi pressure washers, bearings dry out and parts rust. The real test of a used bike is not how shiny it is but how well it has been maintained and what kind of mechanical shape it's in. The purchase price is only a part of the cost of restoring a used bike to operating condition. It is not unheard of for unsuspecting buyers to spend more on parts and repairs than on the machine. How can you tell if a bike really is in good shape, not just good-looking? Following are 10 clues to help you avoid buying a lemon in disguise.1. Overall ConditionWhen you go to look at a bike, first pay careful attention to everything besides the bike. Is the garage clean and organized? In what condition is the owner's truck? Does the owner take pride in his stuff? These insights will give you an idea of how your potential new mount has been used and maintained, and they are much more important factors than new graphics. Look toward that inner beauty. Items to note are mangled radiators, smashed frame loops and a rear subframe that doesn't line up with the rear wheel. A radiator costs big, so make sure it isn't on the verge of leaking from stress bends. These are signs of major abuse and frequent crashes. Do a quick check of the condition of the tires and wheels. A set of tires, rims or replacement spokes can be expensive. Also note wear on the frame paint and on the footpeg teeth and pivots, to determine how much the bike has really been ridden.2. Wheel BearingsEven sealed bearings wear out. Under ideal clean and dry conditions, it can take millions of revolutions, but for dirt-bike wheels, clean and dry don't apply. Put the machine on a stand so both wheels are off the ground. Rotate them and listen for any squeaks or grinding noises. Test for any side-to-side movement of the wheel relative to the swingarm or fork. Grab the wheel directly above the axle and, while supporting the bike with one hand, forcefully push the wheel to the left and right to feel any freeplay. There should be zero freeplay, and any movement means that wheel needs new bearings. Expect to pay between $15 and $30, not including labor, to replace bearings. Don't even bother replacing bearings without also putting on new seals; and this may require purchasing new spacers. You could spend more than $100 per wheel to ensure they are safe. If there is a lot of play, pull the axle and check carefully for any hub damage, as you could spend at least another $200 to $300 for a replacement hub if the bearing bore is worn out.3. Steering-head BearingsThis bearing is most susceptible to pressure washing but can also be ruined by a poorly routed gas-cap vent hose. Standing in front of the machine, grab the bottom of both fork legs and try to move them back and forth, perpendicular to the fork legs. If there is any play, plan on new bearings and seals and at least another $100 investment. While you are at the front of the bike, see if the fork turns easily side to side with no binding. Also, check the steering stop. If the triple clamp or the tab on the frame are damaged, that is a sign of a big crash that might have damaged the frame.4. BrakesSqueeze the brakes and check their firmness. Mushy is bad and can indicate poor maintenance or even a worn-out master cylinder. Ka-ching! A quick look will tell you if there is any brake pad left, but you'll also want to check the overall system. Grab the caliper, especially the rear, and check for any side-to-side play. A bit is normal, but a lot can be dangerous; it may require replacing the sleeves or, in the worst case, buying a complete caliper. Also, check the rotors for straightness by spinning the wheel while holding something (a key will do) on top of the swingarm or on the front of the fork leg to see if the rotor is bent. Additionally, an extremely worn rotor is a sign of heavy use and can be a precursor to other, more-significant wear and tear on the bike.5. SuspensionWhile you won't be able to do a comprehensive analysis of the fork and shock, there are a couple of quick tests to evaluate the relative condition of these components. First, look for any obvious fork-seal leaks. Scan the bottom fork casting for any signs of oil buildup. On some bike brands, you can also slide the wiper out of the fork leg and inspect for buildup of mud and oil. Another important check is for worn bushings in the fork. With the bike on the ground, lock the front wheel with the front brake; and by pushing down and forward on the handlebar, you will be able to feel some freeplay if the bushings are worn. Make sure you have first evaluated the wheel and steering-head bearings as they will give the same feel. You can also do this by grabbing the bottom of the fork legs in the same way you tested the steering-head bearings. Expect to spend some major bucks to repair the fork if any noticeable play is felt during these tests. To check the shock, push up and down on the rear of the bike and note any damping. If the bike boings back up, steer clear, as the shock is probably worn out. Also check for freeplay at either end of the shock, indicating worn bushings. A shock rebuild can easily top $500, so be thorough in this evaluation.6. Swingarm PivotAnother bearing that is very susceptible to damage from the pressure washer is the swingarm pivot. A definitive test is to remove the shock and move the swingarm through its full travel, but most likely, the current owner won't allow you to do that much work. Nonetheless, sit on the bike and make the rear suspension move, listening for bad sounds. Also, with the bike on a stand, grab hold of the end of the swingarm and try to move it left to right. This will take some force, so have someone hold the bike; but if there is any freeplay, new bearings are in order, and again you're looking at give or take a C-note for repairs.