Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: billywingnut on February 12, 2019, 08:30:47 PM

Title: Battery Voltage
Post by: billywingnut on February 12, 2019, 08:30:47 PM

After doing some checks on my bike I am puzzled by some of the voltage readings I have found.
My battery stands at 12.6 volts when ign is off.  I switch on ignition it drops to 11.8 volts with engine  not running.
When I check the voltage on the black and white connectors under the tank that feeds the contact breakers, it is showing  10.6 volts with the wires to the contact breakers disconnected, A loss of over 1.2 volts.
The battery has been charged and is 18 mths old.
What I would like to know is where is that 1.2 volts being lost, is that normal? 
The bike runs ok but I believe the spark could be  stronger.

Title: Re: Battery Voltage
Post by: Bryanj on February 12, 2019, 08:51:57 PM

Dirty bullet conectors and/or kill switch connections.

Title: Re: Battery Voltage
Post by: Trigger on February 12, 2019, 09:05:32 PM

Is the drain with the kill switch on or off ? Took me a while to work out that i was losing power to the points  ???

Title: Re: Battery Voltage
Post by: paul G on February 12, 2019, 09:28:10 PM

The 1.2v will be a normal voltage drop due to wiring loom.
The voltage to the coils is not direct and goes via the kill switch. There is a mod not specifically for your bike but in general where a relay is used to take the voltage straight from the battery to the coils and the normal supply to the coils is used to switch the coil on the relay. ;D

Title: Re: Battery Voltage
Post by: SteveW on February 12, 2019, 10:33:45 PM

Quote from: paul G on February 12, 2019, 09:28:10 PM

The 1.2v will be a normal voltage drop due to wiring loom.
The voltage to the coils is not direct and goes via the kill switch. There is a mod not specifically for your bike but in general where a relay is used to take the voltage straight from the battery to the coils and the normal supply to the coils is used to switch the coil on the relay. ;D

That's the same mod as used on old VW busses. I used to have a 1962 WV bus, the battery was in the back with the engine.
The feed to the coils went all the way from the battery to the ignition switch then all the way back to the coil. By the time it got back there it was about 8 volts, probably about 16 feet of cable. Relay next to the battery sorted it.

Title: Re: Battery Voltage
Post by: billywingnut on February 12, 2019, 10:55:03 PM

Thanks for all comments,
 The voltage drop occurs with the kill switch stripped out  so I guess it must be bad connection at ign switch or plug/socket.
What I was trying to determine is whether this drop is normal for this model. or is a fault on my bike.
Has anybody checked the voltage on points ( when open) and if so what do you get.

Title: Re: Battery Voltage
Post by: paul G on February 13, 2019, 12:20:27 PM

Your still going all the way up to the headlamp bucket and back.
You WILL see a voltage drop  ;)