How A 2-stroke Reed valve works.

A reed valve is simply a one way valve that lets the air/fuel mixture from the carburetor into the crank case during vacuum.

In case you need them, you can get new reeds here →

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When under pressure, the reed valves close to allow the fuel mix in the crankcase to be forced up into the cylinder.

The reed valve also atomized fuel as much as possible as it enters the crankcase. Better atomization = more power.

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14 COMMENTS

  1. hi mate my sons ktm50 is and pain to start and whn it starts it runs bad ive turnd my reeds over this mean there no good

  2. I've got a ktm exc 125 with boysen reed valves which are very slightly stuck open. Could this cause the engine to splutter at mid range to top end?

  3. Alrighty man thanks for the reply I had Bowen super stock carbon reeds and they just broke not to long ago I. Going to try the fiber reeds this time around

  4. I have just done one simple test on my brand new KTM which has small gaps on the reeds. I disasembeld air filter and started engine. I was watching the carburetor intake side during slight throttle opening. I also opened choke to richen mixture.

    I saw fuel mixture coming back to the air filter box at slow rpms.

    I did the same test on Beta with V-Force. The result was the same. I don't know if the reeds have gaps but I going to check it.

    So both bikes don't have good tight reed valve or a little of moxture can go back to the airfilter side and it is normal?

    Any suggestion?

  5. I have been having bogging problem when full throttle in 4th and 5th gear on 2003 cr250. do I need new reeds?

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