Honda-SOHC
Other Stuff => Misc / Open => Topic started by: SteveW on August 16, 2019, 01:11:27 PM
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Right, you are all going to think this is my imagination and i'm going crazy but here goes:
74 CB550, has electronic ignition and a solid state regulator / rectifier all new. New bog standard lead acid battery.
Bike starts on the button, rides fine.
If I don't use it for say 2 to 3 weeks, when I put the key in the ignition and turn it on (just on, no attempt to start it), the bike makes a brief hiss then wont do it again.
Bike fires up perfectly, idles fine, rides fine.
The hiss noise will not come back for a least a couple of weeks if the bike is not used.
Hiss is nothing to do with the fuel tank, petrol tap is off when it happens.
Just wondered if there was some kind of valve in the battery maybe to release pressure?
It sounds like it comes from below the seat so i'm thinking battery. Battery is fine, holds a charge.
Please, no Snake comments :P
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Is it a hiss? Or a buzzz.
On my 500.when I switch on.I get a click from a solenoid. Under the l/h side panel.
It may be this.
Round alloy tub.maybe indicators flasher unit.
Take side panel off.and check when you switch on/off.
My best guess
Sent from my SM-A750FN using Tapatalk
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Check all your electrical connections in the area of the noise it could possibly be a connection arcing.
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It could be a partial petrol ignition?
With electronic ignition you will very often get a spark generated when you switch the ignition on which can/will ignite any petrol or fumes which may be the cause of the slight 'hiss'? I often have this happen on my Suzuki GT 750, but must admit have not experienced it on my CB750 which is also fitted with electronic ignition.
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Definitely a hiss, like if you press your finger on a tyre valve.
But it will only do it if the bike has not been used for 3 weeks or so.
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You'd have to get ready when you think it's going to do this to at least pinpoint the source "sealed" batteries have to be able to vent in order to prevent extreme pressure build up.
They are designated VRLA "valve regulated lead acid" type, and just maybe what you hear if you have this type.
https://en.m.wikipedia.org/wiki/VRLA_battery
Link gives overview.