For the used motorcycles, check the condition of the gears, the teeth should not tilt to one side shark fin. If so, the gear is worn out. For the front sprocket you often have to unscrew a cap to get a view of it. The chain should not be rusty and should actually look well lubricated. Also check the rear of the sprocket to see if the chain is properly seated and is not pulling too much to one side e.g. due to a slightly skewed rear wheel after incorrect adjustment.
In case of harley davidson you can try to pull the chain backwards at the rear sprocket, if you can pull more of the chain than one link slightly from a tooth, then the chain is worn out. Have someone sit on the engine and check the free play in the center of the chain bottom. This may have 2-3cm clearance, if this is too much, you can still adjust the chain, but if it is already set all the way back, you need a new set. Since most 11kW / 35kW engines do not have a belt or gimbal, we may return to this later. A motor scooter V-belt usually needs to be replaced every 10,000km.
Check the frame for rust. A little rust won’t hurt. Also check if no other color has been sprayed anywhere and look for color difference. This could indicate a repair. See if the frame and frame tubes are straight. You can often see this when you stand behind or in front of the motorcycle. If you are behind it, immediately check whether the front wheel and rear wheel are in line. If not, it could indicate a crooked front fork or a crooked frame. Also in this case it is better to look for something else.
Suspension (front and rear) and head clearance
Front fork: Test the front and rear suspension, squeeze the front brake and push down hard on the handlebars several times. The suspension should go smoothly, should not get stuck, and should not sway for too long. Check the front fork rubbers, they must be dry and clean and not leaking oil. The fork must also be dry and free from rust, pips and other debris. Also keep this clean after your purchase to avoid leakage.
Rear spring: If the motor with the rear wheel is on the ground, you can let someone hold the motor. Then stand to the left or right of the swingarm where it is easiest to grasp the swingarm and move it towards and away from you. There should be no play here. Otherwise those swingarm bearings are worn. To test the rear spring, stand back to the bike and push firmly on the saddle a few times, it should come back smoothly and not get stuck. Pay close attention to the spring or springs that there is no oil leakage there either.
To check the steering head play of the steering wheel, do the following:
Turn the steering wheel from left to right and back and forth a few times. This should go smoothly and smoothly, without the feeling of a nod. Have someone sit on the motorcycle sit in front of the motorcycle then pull the front fork towards you and away from you, there should be no play in this.