O-Rings

Is an AN fitting dripping, or do the dowel pins in the cylinder head need new seals after a teardown? This subcategory contains individual O-rings for engines, hose fittings and forks. The category is for you if you know the size of the joint you need to seal.

What the O-rings in this category are used for

An O-ring seals by being compressed in a groove between two surfaces. Among the O-rings in this category you will find, for example, O-rings from Cometic Gasket for Harley-Davidson Twin Cam and EVO, including for cylinder head dowel pins, starter to engine case and breather bolts. There are also O-rings from Fragola for radius fittings in -6AN and -8AN, a multipack from Radium Engineering in 6AN/8AN/10AN and O-rings for the compression piston in KYB forks. Fel-Pro, S&S Cycle and Vibrant are other brands in the category.

How to choose the right O-ring

• Size: Inner diameter and cross-section, or AN size and thread, e.g. 9/16-18 or 3/4-16.
• Material: Whether the ring can handle oil, fuel or coolant depends on the material and the medium. Check the information for the specific product, e.g. fluorosilicone.
• Hardness: A rating such as 70 duro affects how the ring compresses and handles pressure. Follow what the joint is designed for.
• Quantity: The rings are sold individually or in packs of e.g. 10 or 25 pcs.

If you need many different sizes, a set from O-ring kits can be more practical.

Installation and maintenance

Clean the groove and lightly lubricate the O-ring with a lubricant suited to the material and the fluid. Avoid rolling or twisting the ring over sharp threads, as it can be damaged. An O-ring that is flattened, cracked or hard typically seals less effectively. So replace it whenever the joint is apart anyway.

Frequently asked questions

Can I reuse an O-ring when I take a joint apart?

It is typically not recommended. A used O-ring has often taken the shape of the groove and may have hardened, so it seals less effectively when reinstalled. On dowel pins and breather bolts, for example, it is easy to replace it at the same time.

What does 70 duro in the product name mean?

It indicates the O-ring's hardness on the Shore A scale. Hardness affects how easily the ring compresses and how it handles pressure. Use the hardness specified by the manufacturer or the original part for the joint.

Why are both AN size and thread listed for O-rings for fittings?

The same AN size can come with different threads, e.g. -8AN with 3/4-16, 7/8-14 and 9/16-18. The O-ring must match the thread of that specific port, so check both sizes before you order.