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Product details
The PMO mixture screw O-ring, part PM-O164-0, is the seal on the idle mixture screw of a PMO carburetor that stops outside air from leaking past the screw threads into the idle circuit. The idle circuit runs on high manifold vacuum, so a small leak at one screw adds air the idle jet never metered. The usual signs are a lean, unsteady idle on one barrel, or a mixture screw that barely changes the idle when turned. An O-ring that has hardened, flattened, or been nicked by the threads will not seal.
PMO also packs these O-rings into its carburetor rebuild kits. The 40mm (PM-O700-0), 46mm (PM-O700-1), and 50mm (PM-O700-2) kits each contain 12, along with gaskets, needle valves, float shims, washers, and an accelerator pump cam. If the screw tip is worn, add the PMO idle mixture screw, PM-O162-0.
Technical Details
- Manufacturer: PMO (EMPI)
- Manufacturer part number: PM-O164-0
- Location: idle mixture screw, one per barrel
- Matching screw: PMO PM-O162-0
- Also in: PMO rebuild kits PM-O700-0, PM-O700-1, and PM-O700-2 (12 per kit)
- UPC: 707924551945
Fitment & Compatibility
Made for the mixture screws on PMO 40, 46, and 50mm carburetors for air-cooled Porsche flat-six engines, and sold for Weber carburetors too. On a Weber, pull one mixture screw first and confirm it uses an O-ring seal.
Installation & Tuning Notes
Count the turns from lightly seated as you remove each screw. Wet the new O-ring with clean oil, thread the screw in gently, and reset each barrel by ear after synchronizing.
Common Questions
How many do I need for both carburetors?
One per mixture screw. A pair of PMO three-barrel carburetors has six screws, so six O-rings.
Do the rebuild kits include these?
Yes. Each PMO rebuild kit, 40, 46, or 50mm, includes 12.
