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Product details
The PMO idle mixture screw, part PM-O162-0, is the adjustable needle that sets how much idle mixture each barrel of a PMO or Weber three-barrel carburetor delivers on an air-cooled Porsche flat-six. Each barrel has its own screw, so a pair of three-barrel carburetors carries six. Turning a screw in leans that barrel's idle mixture, and backing it out richens it. A screw with a bent or chewed tip no longer meters smoothly, which is the usual reason to replace one.
Tip damage almost always comes from running the screw down hard against its seat. On PMO carburetors the screw seals in its bore with an O-ring, PMO part PM-O164-0, so order one with each new screw. PMO's 40, 46, and 50mm rebuild kits each include 12 mixture screw O-rings but no screws, so a damaged screw is bought on its own.
Technical Details
- Manufacturer: PMO (EMPI)
- Manufacturer part number: PM-O162-0
- Part: idle mixture screw, one per barrel
- Seal: O-ring, PMO PM-O164-0
- UPC: 707924552652
Fitment & Compatibility
Sold for PMO and Weber carburetors on air-cooled Porsche flat-six engines. Weber has used more than one mixture screw design, so compare the thread, length, and tip of your old screw before ordering a set.
Installation & Tuning Notes
Seat the screw lightly, never forcing it, then back it out and find the smoothest-running point in quarter-turn steps by ear. Set mixture last, after timing, valve adjustment, and synchronization.
Common Questions
Which way do I turn the mixture screw to lean it out?
Turn it in (clockwise) to lean the idle mixture and out to richen it.
Do I need a new O-ring with the screw?
On PMO carburetors, yes. Fit a new PM-O164-0 whenever the screw comes out so the idle circuit stays sealed.
