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▷▷ 2021 ▷ Troubleshooting a reed valve of a two-stroke engine

5 julio, 2021

troubleshooting twostroke engine reed valve

by Tom Lutzenberger

Motocross Image by Jerome Dancette from

Reed valves on a two-stroke engine tend to be somewhat temperamental, as the inner workings of the assembly are very sensitive. If parts are damaged or worn, they can immediately impact the carburetor air / fuel mixture, impairing engine performance. However, reed valves are often worth the time it takes to troubleshoot, as the design cuts back flow and makes carburetion more efficient on a two-stroke engine. Solving many of the problems with reed valves includes eliminating other problems that could cause failure.

Step 1

Start the engine of the motorcycle or scooter and run it, if possible. Wait about five minutes for the engine to warm up. Hit the gas pedal to see if the carburetor responds correctly and quickly. Turn off the motor. Turn off the fuel supply.

Step 2

Use a screwdriver to disconnect the banjo clamp that secures the carburetor to the intake hose that connects to the engine reed valve manifold. Pull the carburetor free and disconnect the fuel line attached to the side. Use a wrench to disconnect the fuel line.

Step 3

Hold the end of the fuel line in your hand with a rag and slowly turn on the fuel supply to see if the fuel is flowing properly. Turn it off when fuel begins to spill onto the rag.

Step 4

Lay the carburetor and fuel line aside. Unscrew the banjo bolt holding the intake hose to the reed valve manifold. Set the hose and clamps aside. Look inside the reed valve manifold for any signs of damage to the inner petals of the reeds. Use a socket and socket wrench to remove the intake manifold from the engine.

Step 5

Separate the reed valve manifold by hand once it is loose from the engine. Take out the old reed petals and replace with a new set. Screw the reassembled manifold back onto the engine with the socket wrench. Screw in the inlet hose clamp after reinstalling the hose.

Reconnect the fuel line to the carburetor and reinstall the carburetor in the intake hose. Tighten the safety clamp on the hose that locks the carb in place. Turn fuel flow back on. Start the engine again and test the response. Take the motorcycle or scooter for a ride to test its performance.


  • Checking the color of the spark plug on your cylinder with a socket wrench can quickly tell you if the engine is running on low fuel (white) or too much fuel (oily black). Proper fuel / air mixture should result in proper spark plug tip color when properly operated (chocolate brown).


  • Do not have flammable sources nearby when working on the engine’s carburetor or fuel line. Gas fumes can easily ignite.

Articles will need

  • Screwdriver
  • Wrench
  • Shop rag
  • Pipe wrench and sockets

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