EC PK875 Stock Appearing Carburetor (Please Read Directions Carefully Before Installing)
Ref Part Number Description Ref Part Number Description 1 Call-in Carburetor Nut 6 PK-875A Methanol Stock Appearing Carburetor 2 339VS or 335VS Filter Adaptor 6 PK-875G Gas Stock Appearing Carburetor 3 DJ-1257 Choke Lock 7 138190052EC PK875 Bore Matching Carburetor Gasket 4 DJ-1257A Choke Lock Bolt 8 PK-INS CNC Bore Matching Plastic Insulator 5 138190053A Air Cleaner Gasket 9 138190050 D-Shape Intake Gasket
Installation.
1. Remove the current stock carburetor, velocity stack, gaskets, and insulator. The EC PK875 has matching replacement parts for optimal performance.
2. Install the D-shape intake Port Gasket, followed by the CNC Plastic Insulation, with the D-shape facing the port and the round port facing out.
3. The carburetor gasket can be mounted only in one way that matches the shape of the carburetor flange—to the insulator.
4. Ensure nothing is blocking the bowl vent on the carburetor, and mount it against the carburetor gasket.
5. Mount the Air Cleaner Gasket and Air Filter Adaptor. Make Sure the Adaptor is mounted so it doesn’t block the air correction jets.
6. Torque the Carburetor Nuts to 6 ft/lbs
7. Mount the Air Filter. We recommend using the 641 or 641EC Air Filters. Make sure the air filter is clean and not over oiled. A dirty air cleaner or over oiled air filter may restrict airflow and cause the carburetor to go rich and erratic.
8. Attach the Fuel Line to the carburetor. You may need a ¼” to 3/16” hose adaptor to attach the fuel line. Otherwise, you may create an air leak that makes erratic carburetor tuning and performance.
9. Attach your stock or aftermarket top plate linkage throttle rod to the carburetor.
10. The carburetor is ready to start. If the engine requires choking on cold starts, use a plastic bag and cover the air filter tightly. The bag will create enough vacuum to pull fuel through the carburetor. After the initial start, the engine should start much more effortlessly.
Fuel Tank Vents
Fuel tank vents should be checked before your carburetor is mounted. You should have a vent with a 1/4-inch hole in your fuel tank. DO NOT USE CHECK VALVES on the end of a 1/4 hose, as these restrict the vent and may not vent at all. Venting issues can range from pressurizing fuel, causing a rich condition, or creating a vacuum, especially after running, creating a lean condition. We’ve covered this thoroughly in our “Your Fuel Tank Sucks and It’s Costing You Performance” Blog.
Fuel Pump and Pulse
Use only use our TFPC-1 or TFPC-2 Round Pump or OE Walbro round pump. Do not use any square, Briggs lawnmower, or 2-cycle pumps. The incorrect fuel pump can significantly affect the tune and performance of the carburetor.
Pulse the fuel pump from the crankcase. Pulsing off the valve cover may cause the carburetor to go lean on the top end.
Exhaust
We recommend using no less than .900 ID headers, ideally .960-.990 ID. If possible, no muffler will offer the best performance; if a muffler must be used, it must have an ID larger than the pipe with as few baffles as possible—no threaded or lawnmower-style mufflers. Small headers and restrictive mufflers may require extensive carburetor tuning.
Tuning
Our carburetors are tuned to be in the range of most engine combinations. Changes in elevation and weather conditions may require additional tuning.
DO NOT replace the main jet unless absolutely necessary. The floor around the emulsion tube is fragile, and you could potentially damage the carburetor if you over-tighten the main jet. Due to this, we have a set screw holding the emulsion tube. Do not attempt to remove the emulsion tube. If you need to adjust, the main jet takes extra precautions when doing so. We offer no warranty of any kind, and if damage occurs, we offer no support or suggestions for repairing the carburetor.
Fuels
Your stock appearing is built specifically for your type of fuel. Gas carburetors cannot be converted to methanol, and methanol carburetors cannot be converted to gas with jet changes alone. Do not ask for or attempt this type of conversion. The blueprinting required is explicit for each fuel.
Stock Appearing Gas
Pump or Race Gas is acceptable except for fuels with oxidizer additives. Oxygenated gasoline or accelerants may cause the engine to run lean.
Stock Appearing Methanol
For any methanol carburetor, it is crucial for you to flush the carburetor after every race. No exceptions! Flushing not only preserves the carburetor but also helps protect and maintain your engine from corrosion and oxidation.
We recommend flushing your entire fuel system from the fuel line off the fuel tank through the fuel pump, carburetor, and engine while it runs. Starting with the fuel line will run all the methanol out of your fuel system and engine. We recommend using 8-10oz of Marvel’s Mystery Oil to 1 gallon of non-ethanol gasoline.
Remove your fuel line from your fuel tank and attach it to your gas mixture. Start your engine and allow it to run until it spits and sputters. Usually, your engine may stop running due to the rich gas mixture, but if it doesn’t, by the time it spits and sputters, you can shut down the engine. Pull your recoil until the engine is back on the compression stroke to ensure both valves are closed.