PMO Throttle Return Spring for PMO and Weber Carburetors

The PMO Throttle Return Spring (PM-O128-9) is the spring that pulls the throttle back to its idle stop when you lift off the pedal on a PMO Induction carburetor setup. PMO carburetors use a one-piece stainless steel throttle shaft, machined and micro-polished to a .002 inch tolerance and carried in oversize ball bearings, and the return spring supplies the closing force. A stretched, rusted, or broken spring lets the throttle hang open or creep back to idle, which is a safety problem. It is priced each.

PMO's throttle linkage kits, PM-O918-0 for PMO carburetors and PM-O919-0 for Weber carburetors, do not list a return spring, so it is ordered on its own. A slow-closing throttle can also be a linkage problem, so before replacing the spring, work the linkage by hand and check the bell crank, ball pins, and bearing arms for binding.

Technical Details

• Manufacturer: PMO Induction (EMPI)
• Manufacturer part number: PM-O128-9
• Part type: throttle return spring
• UPC: 707924555646
• Sold as: each

Fitment & Compatibility

For PMO Induction carburetor and linkage installations in 40mm, 46mm, and 50mm sizes. Spring length and hook style are not published, so compare against your existing spring, especially on a Weber setup.

Installation & Tuning Notes

With the engine off, open the throttle fully at the carburetors and let go. Both carburetors should snap back to their idle stops every time. Repeat the check after any linkage or synchronization adjustment.

Common Questions

My idle hangs high after I lift off. Is it the spring?
It can be. Check the spring for stretch first, then look for linkage binding, and rule out an intake air leak, which also raises idle speed.

Does the PMO linkage kit come with a return spring?
The published contents for PM-O918-0 and PM-O919-0 do not list one.