Kuryakyn Engine Crankcase Breather Cap Bolt

Kuryakyn Crankcase Breather Cap Bolts: Precision Meets Performance

When it comes to keeping a Harley-Davidson engine breathing correctly, every component matters — right down to the bolts that hold the crankcase breather system in place. Kuryakyn has been a trusted name in the V-Twin and cruiser community since 1989, and their approach to even the smallest engine hardware reflects the same commitment to quality that has made them one of the most recognized aftermarket motorcycle brands in the world.

What Is a Crankcase Breather Cap Bolt?

The crankcase breather system is responsible for venting blow-by gases from the engine crankcase back through the intake, helping to maintain proper internal pressure and protect seals and gaskets from premature wear. The engine crankcase breather cap bolt is the hardware that secures the breather assembly to the rocker box or engine case — a seemingly simple piece that plays a critical role in keeping the entire ventilation circuit sealed and functioning correctly. A loose, stripped, or incorrect-length bolt can result in oil leaks, poor engine performance, or a compromised breather system.

Kuryakyn's Breather Bolt Lineup

Kuryakyn offers breather bolts designed to work seamlessly with their own Crankcase Breather Kit ecosystem, which has long been a go-to solution for Harley-Davidson owners looking to upgrade or restore their engine's ventilation. Key offerings in this category include:

• Part No. 9976 — 1/2"-13 x 1-3/4" Breather Bolt: Designed specifically for 1999–2017 Harley-Davidson Twin Cam motorcycles, this bolt is engineered to the precise thread pitch and length needed for proper engagement and sealing in Twin Cam applications.
• Part No. 9927 — 1/2"-13 x 1" Breather Bolt: A direct-fit replacement for Evolution Big Twin (1993–1999) and Sportster XL (1991–2019) models, sold as a pair and finished in silver for a clean, factory-compatible appearance.
• Part No. 2000 — 1" Replacement Breather Bolt: A dedicated replacement component for the Kuryakyn Crankcase Breather Kit for EVO engines, also compatible with Kuryakyn Hypercharger kit installations where the bolt serves as a critical holding piece in the air cleaner assembly.

Why Choose Kuryakyn for Breather Hardware?

What sets Kuryakyn's breather bolts apart from generic fasteners is their model-specific engineering. Rather than offering a one-size-fits-all bolt, Kuryakyn engineers each variant to match the exact thread specifications (1/2"-13 coarse thread) and lengths required by the particular engine generation and breather kit configuration. This matters because using an incorrect-length bolt in a breather assembly can result in inadequate clamping force, gasket failure, or interference with the air cleaner bracket. Kuryakyn bolts are also designed to work in tandem with Kuryakyn's own gaskets and adapters, ensuring that every element of the breather system functions as an integrated unit rather than a collection of mismatched parts.

Whether you're refreshing an aging breather system on a classic Evolution-powered Softail or maintaining a Twin Cam Touring bike, Kuryakyn's breather cap bolts are a reliable, application-specific solution from a brand with decades of Harley-Davidson expertise behind it. Browse the full Kuryakyn brand catalog or explore all engine crankcase breather cap bolt options to find the right fit for your machine.