Better known as the Fatboy, Harley-Davidson's FLSTF softail cruiser has long been a popular choice for bikers who want a ride that's muscular yet comfortable. Regular maintenance is required to keep the Fatboy's high-performance V-twin engine humming. Oil and fluid checks are recommended every 1,000 to 2,000 miles, but checking the oil is so easy, you should do it prior to every major ride.
Place the motorcycle on a vertical stand or sit on the motorcycle and tilt it upright. Start the motor and let it to warm up for a few minutes to reach operating temperature. This will allow the oil to heat up and expand slightly. Hold the bike fully vertical to pull oil from the engine's sump for an accurate reading.
Stop the motor and remove the oil tank dipstick. Clean the dipstick and reinsert it completely into the oil tank filler neck. Remove the dipstick again and check the oil level marked on the stick. Add oil as needed and replace the dipstick securely. The oil level should be almost even with the bottom edge of the filler neck.
Remove the dipstick on the transmission, clean and reinsert it completely. Remove the dipstick again and check the transmission oil level. Add oil as needed and replace the dipstick securely.
Remove the T-40 bolts that secure the round derby cover to the primary cover and remove the derby cover. Look into the primary through the derby cover port to check the primary fluid level. The primary fluid should be level with the clutch basket. Add primary fluid as needed and replace the derby cover.
If your Fatboy does not have a dipstick, check that the oil level is just even with the bottom edge of the oil tank's filler neck. Refer to your owner's manual for specific details such as oil type and quantity. If you do not feel confident you can complete this task, have the work done by a qualified technician.
Do not overfill the oil tank, which can cause oil to blowout through the air filter.