How to Add Fork Oil to an RT100
The Yamaha RT100 is a youth-model off-road motorcycle. The low seat height and benign power delivery make it ideal for kids learning to ride off-road. The RT100 has simple cartridge-style forks. The springs in the forks provide support for the front of the bike, while fork oil is used for damping. The correct level of oil is necessary for proper damping and ride quality. Fork oil level is best checked while the forks are off the bike, but can also be checked with the forks still installed.
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Things You'll Need
- Adjustable wrench
- 10W fork oil
- Safety glasses
- Metric ruler
- Helper
- Shop rag
Instructions
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1
Loosen the fork caps with an adjustable wrench. You may need to stand in front of the motorcycle and straddle the tire to hold the forks steady as you break the fork caps loose. Remove the fork caps one at a time. Be sure to hold your hand over the fork cap. The fork spring is still compressed and may shoot the fork cap at your face or across the garage if you are not careful.
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2
Gently lower the front end of the motorcycle until the suspension bottoms out, using your helper for assistance. Have your helper support the motorcycle in an upright position.
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3
Remove the fork springs and set them aside. Lay them on shop rags and make sure they do not pick up dirt or contaminants. Use a metric ruler to measure down from the top of each fork to the oil. The correct fork oil level is 120 mm (12 cm). If the oil level is low, slowly pour in 10W fork oil until the correct level is reached.
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4
Slowly lift the motorcycle and extend the forks. Compress and extend the forks several times to bleed out any trapped air bubbles.
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Reinstall the fork springs, then reinstall the fork caps. Be careful to not cross-thread them.
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Tips & Warnings
Always use motorcycle-specific fork oil of proper viscosity. Motor oil is not the same as fork oil.
Always wear safety glasses when servicing the forks. The fork's springs are compressed, even when the forks are fully extended. If you are not careful, the fork caps, springs or fork oil can fly into your face.
References
- Photo Credit Jupiterimages/Creatas/Getty Images
