Tech Tip Tuesday: Evaluating A Used Dirt Bike

Brand New Motorcycles

While most of would prefer owning a brand spanking new dirt bike off the showroom floor like these, many of us don’t have the funds or the justification for paying for a brand new dirt bike. Today’s tech tip will address some common things to look at when shopping for a dirt bike or evaluating your own to help estimate repair costs.

Spark Plug: The spark plug is one of the best indicators of the condition of the engine. Anything other than a clean lightly brown plug denote there are probably some issues going on with the engine. Some of things to look for are globs of aluminum or buildup on the plug, heavy carbon buildup, a glazed finish, or any surface damage to the plug. Black or ash colored plugs may indicate a rich or lean fuel mixture.

Compression: If you have access to a compression tester, check to see if the compression is above 150psi (2-stroke). Do this by threading it into the spark plug hole, hold throttle fully open, push in kill button, and kick the engine over several times. If compression is far below 150psi, it is probably in need of a rebuild.

Dirt Bike Air Filter

Air Filter: The condition of the air filter is often a reflection of how well someone takes care of their bike. Check for tears, crank case oil, or holes.

Frame: Check frame underside for bent or smashed tubes, cracked shock clevis, or bent linkage. A new frame could be expensive to replace, but some may be fairly inexpensive to repair if you are willing to strip down the frame and bring it to a welder.

Suspension and Shocks: Check front and rear Non Leaking Front Forkshocks/forks for oil leaks. Check chrome and surface for pitting, peeling, dents, or signs of overheating. Compress front forks and check for normal movement and no oil leaks. Front forks cost around $200 to replace just the seals. Sit on the bike and bounce up and down to check rear suspension for normal movement and no strange noises due to bad bearings, bushings or seals.

Bent Kawasaki Radiator Cooling System: Check the coolant level and color of coolant. Brown, gray, or foamy coolant indicates a bad water pump seal or head gasket leak. Check to make sure coolant doesn’t leak anywhere while bike is running and there are no green or white residue around engine. Inspect radiator for crash damage.

Wheels and Brakes: Place the bike on a stand and grab each wheel with your hand. Try to move it side to side and check for any free play in the bearings. Check brakes for deep scratches or signs of overheating. When riding the bike, check for Good Brake Disc and Pad pulsating when applying the brakes. Afterwards check all the lines and hoses for any leaks.

Drivetrain: Check that clutch action is normal and tight when riding. Make sure clutch doesn’t slip when engine is revved in gear with clutch pulled in. Visually inspect chain and sprocketsGood Motorcycle Chain and Sprocket for worn teeth and chain slack. If slack varies greatly at several different points, chain and sprockets will need to be replaced.

Throttle response: Ride the bike in second gear at 1/4 throttle and give it a quick snap of throttle. If it bogs down or dies, it most likely has carburetor issues. Check for a steady and smooth idle and a working choke.

Keep in mind that there are not a lot of used bikes that are perfect, so if there are some issues with the bike, factor the cost of repair when considering its worth. By taking time to thoroughly inspect a dirt bike, you can save yourself from ending up with a lemon that may cost you a lot more than you bargained for. If the seller is aware of some problems but is willing to compensate for them by dropping the price accordingly, you may be able to get a good bargain on a bike that needs a little fixing. If so, don’t forget that GearHead is your OEM parts headquarters with helpful parts diagrams to easily locate the exact part you need. Good luck and be safe!

Have a tech question you need answered? Email us at techtips@gearhead.com

Motocross Race - Jack

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