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Electrics working when revving


DJYAM
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Hi,

My DT 125 MX has a strange problem. The electrics, indicators, horn and brake lights only work when the bike is being revved quite high. This seems like the battery is not charged, or might be knackered.

The only thing is, the headlight works whilst at tickover... It gets slightly brighter when revved but unlike the horn and other lights, doesn't die on tickover.

Sound like a battery problem or a bigger fault?

Thanks in advance

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Check the battery./Main fuse./Electrolite level.

 

Its got to be really shagged to do nothing.

 

 

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Don't have access to a voltmeter at the minute, the battery seems to produce voltage though as the lights and bits work at higher revs.

The electrolyte level is between the two markers on the left hand section, full on the middle and at the low line on the right side. 

Is the fuse in the little white ccontainer in the positive line? Just checking that now. 

An update.

Just looked at the fuse, upon visual inspection it seems broken.

Does this explain the electrics working at high revs though? Do they not use the battery when running?

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The battery acts as a store of energy. The bike generates its electricity much the same as a car does. The battery fills the gaps in. When you change gear, stop start traffic riding at night. These are times when the engine cannot make sufficient electrical energy efficiently.

You have to remember that bikes don't have massive charging systems as they cost horsepower. 125's don't have anything to spare. Would you give up 20% of your power for brighter indicators, and carry another 5kg of battery and the associated cosmetic implications? didn't think so.

Because of that the bike relies on the battery more than a car does, without the battery the lights and such will act as you say, but! without the battery to stabilise the electrical system there will also be voltage spikes when you have that red mist moment at 10000rm and you electrical system will cop for 15v and then you blow bulbs.

 

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So I put the fuse in last night, electrics working well when not running. 

Start her up this morning and a smell a VERY strong plastic burning smell. 

Under the tank on the left side, a terminal was melting plastic. The terminal has 2 red wires and 1 white going into it. 

The terminal is clipped onto two pipes, leading to the engine casing and the oil tank, just breather pipes. 

Any help much appreciated. 

 

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Sounds like the rectifier to me too. Nothing else electrical under the tank.

As said. Need a picture.

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Thanks for all the help guys. 

Could this be caused by another fault or is it just the voltage rec just knackered and burned out?

Cheers

Sometimes they just die, my voltage regulator did the same at the mot a few years ago. Remember this stuff is 30 years old and 30 years ago we weren't as good at components.

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Sorry to revive this old post, Just updating. 

Voltage regulator swapped and working. 

Just bought a new bulb for the neutral light, it won't come on still. The bulb works as I put it in the indicator flasher and it works. 

Could this be the socket broken?

Cheers

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If it works out of the socket then probably yes it's the neutral light socket that's at fault, can you change it ? Or you could just rewire it externally, one wire up the side and one soldered to the bottom.

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