Fast Eddie
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- Oct 4, 2013
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There is another maintenance topic with these carbs.
The float needle housing O ring, #37 in the diagram above, can perish over time (no doubt exacerbated by ethanol fuel).
When this happens, fuel will pass by the O ring, thus bypassing the float valve, thus causing flooding. This would cause excess fuelling at low throttle openings and could therefore cause idle issues. At bigger throttle openings, the fuel will be used and the float level will therefore drop and be ok.
This is also why these carbs should never be left with the fuel taps on IMO. If the taps are left on and you have a leaky O ring, then due to the design of the carbs and the angle they’re mounted at, and if your filter stubs are designed to divert air to the pilot circuit through the air filter, then fuel will basically fill up the carb and enter the inlet port where it will then run down the port and into the engine.
To further complicate this issue, the O ring is specific to this application and is a smaller section than standard O rings. Standard o rings will not fit, and if you force them, will cause the housing to be cock-eyed, or the O ring to be damaged, or both. Even some rebuild kits from specialist (inc a certain well known U.K. supplier) include the wrong o rings for this !
I get my Keihin parts from here, I’ve not had any issues thus far:
The float needle housing O ring, #37 in the diagram above, can perish over time (no doubt exacerbated by ethanol fuel).
When this happens, fuel will pass by the O ring, thus bypassing the float valve, thus causing flooding. This would cause excess fuelling at low throttle openings and could therefore cause idle issues. At bigger throttle openings, the fuel will be used and the float level will therefore drop and be ok.
This is also why these carbs should never be left with the fuel taps on IMO. If the taps are left on and you have a leaky O ring, then due to the design of the carbs and the angle they’re mounted at, and if your filter stubs are designed to divert air to the pilot circuit through the air filter, then fuel will basically fill up the carb and enter the inlet port where it will then run down the port and into the engine.
To further complicate this issue, the O ring is specific to this application and is a smaller section than standard O rings. Standard o rings will not fit, and if you force them, will cause the housing to be cock-eyed, or the O ring to be damaged, or both. Even some rebuild kits from specialist (inc a certain well known U.K. supplier) include the wrong o rings for this !
I get my Keihin parts from here, I’ve not had any issues thus far:
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