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Discussion Starter #1
Hi, does anybody know what the secondary air supply system does? Can you remove it or would you need the engine remapping. Mine is running marginally weak anyway thanks
 

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it injects air into the exhaust to reduce emissions, via reed valves on the head. if you have a bike with SAI then you will not get a true reading from an exhaust gas analyser.
 

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Discussion Starter #3
Secondary Air System

Thanks for the reply, does that mean the bike is running weaker or richer than shown on the exhaust reading?
 

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the SAI will cause the exhaust gas reading to show leaner at idle or when the throttle is chopped. the negative pressure in the exhaust causes the reed valves to open and ingest clean air from the airbox.

how do you know your engine is running weak? how weak is it? under what conditions?
 

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I think you're looking for something that isn't there.

in general terms anything less than 15:1 is rich, more than 15:1 is lean although the tendency is to tune for around 13 iirc. so if 13.6 was the weakest what was the richest? where in the rev range was it lean?

12.5 - 13.3 gives best power - richer still. but you will see variation throughout the rev range.

post a graph up if you have one.
 

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Discussion Starter #7
Sai

Thanks again, as you say I don't think there is anything to fret about, just I didn't know whether to leave it connected or not. The AFR didn't alter much throughout the rev range, ie from about 13.4 to 13.7 thanks for your help
 
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