Dichtungen & Simmerringe

Copper spiral-wound gaskets are the go-to for aftermarket header fitment — they conform to minor face irregularities better than the OEM crush-type and are reusable if you pull the headers for service. Check the port diameter; some Dyna-pattern headers use a bore size that a straight OEM replacement won't seal cleanly.

The OEM 34901-07 set is the default for good reason — the silicone bead on the cover gasket is engineered to the specific Twin Cam primary gap. Drag Specialties primaries are a solid lower-cost alternative, but some builders add a smear of Hylomar on the cover face. If you want zero drama on a messy primary job, the OEM kit is worth the extra few pounds.

A sooty black ring around the exhaust port flange — typically offset to one side — almost always points to the gasket, not the head. Head gasket failures show as oil seeping between the barrel and head, not at the port face. Clean the area, run the bike to temperature, and check: a gasket leak deposits fresh carbon quickly.