Instructions for EC's Pop-Off Gauge for Diaphragm Carburetors

EC Pop-off Service Instructions

Pop-off pressure can have a considerable impact on the performance and consistency of your diaphragm carburetor. Most of the adjustments will affect the carburetor's performance at idle and low-speed acceleration.

Pop-Off Service Instructions

Tools:

• Pop-Off Gauge: POPG-1 0-15psi or POPG-2 0-30psi

• Fulcrum Arm Gauge: 704 Tillotson Alky (Methanol), 705 Tillotson Gas, 706 Walbro Gas, 707 Walbro Alky (Methanol)

• 715 EC Spring & Shim Kit

• Maxima Racing Oils MPPL

Instructions

With the Cap and Pump Stacks on.

1. Remove your fuel line and spray a penetrating oil like Maxima Racing Oils MPPL into the fuel cap of the carburetor. The oil will wet the needle and be closer to the condition it will be when running. Never check your "pop-off" pressure with the carburetor dry.

2. Pump the tester up now and watch for the tester needle to drop. When it does, this is the inlet needle's "pop-off" pressure. A good needle and seat will "pop-off" at the desired setting, drop ½ to 1 pound and hold. A very slow leakage of pressure will not affect the performance of your carburetor. Still, a total drop from the desired setting to zero on the gauge will cause very poor carburetor performance and must be corrected.

We recommend checking pop-off with the pump stacks removed to get more accurate results and diagnose or modify pop-off pressure. 

With the Cap and Pump Stacks off.

1. Begin by removing the pump stacks from the carburetor, as well as the main metering gasket and diaphragm, to reveal the carburetor's internals.

2. Set your fulcrum arm height with the fulcrum gauge. To do this, bend the nose of the fulcrum arm parallel with the carburetor's gasket surface carburetor. Bend the fulcrum close to the fulcrum pin to raise or lower the fulcrum arm height. Resting the gauge on the gasket surface on the side recommended by us for your carburetor makes the fulcrum arm touch the bottom of the gauge.

3. Make sure the inlet needle is free. If the carburetor sits too long, the needle may stick.

4. Spray the Fuel Inlet Needle with Maxima Racing Oils MPPL until it forms a pool around the needle.

5. Your pop-off gauge should have a fuel well-fitting. Attach this to your pop-off gauge and insert this in the fuel well port right above the fuel inlet seat. Ensure it is sealed tightly with the O-ring.

6. Pump your gauge. As you gain psi, make your pumps more gradual. You want to be able to read your pop-off pressure and keep a record of it. 

7. When the pressure overcomes the needle, that is your pop-off pressure. The needle should reseal and hold pressure. If pressure doesn't hold, you have a leak under the needle or under the seat. Clean the needle and repeat your process. If there is a leak under the seat, the seat will need to be removed and replaced.  

8.You can choose to increase or lower the pop-off pressure using different springs and/or shims. In some cases, the inlet springs can be modified. If the spring has doubled flat coil on the end of the spring, one coil can be cut as long as it leaves a full flat circle. If the spring leaves an incomplete circle, the pop-off pressure will be inconsistent on the track. It is not advisable to stretch any inlet tension spring to modify pop-off pressure.

9. Once you have made your checks and modifications, you can reassemble the carburetor.