KE175 B3 Headlamp very dim. (1978)

[Matt Freeman]

Hi guys.
I've fitted a new battery. I fully charged it, it's holding over 6.2volts.
When the engine is running I get over 6.5volts, so it is charging.
All other electrics work well, bright indicators, loud horn etc.
Brake light is also very good.
The headlamp is very dim though.
Both Low and high, they are literally only just glowing.
The headlamp runs directly off the magneto as far as I know because it only works when the engine is running whereas the parking lights operate as long as the ignition is on.

I have double checked that it is the correct wattage 6v headlamp bulb fitted.
Any ideas where to start?
Cheers.

[Islander]

That's 6v electrics for you. To get the equivalent power to a 12v lamp out of a 6v unit needs twice the current which just ain't going to happen. 6v systems are notorious for having dim headlights.

[Matt Freeman]

Sure, but they're not even remotely bright enough to be effective. Just dim amber glowing filaments.

[69chris]

as above, some can be pretty poor and need all the help they can get - have you checked/cleaned all the earth connections you can find ?

[doggone]

Try the bulb connected directly to the battery.
Are you sure it's not a 12v bulb?

[Matt Freeman]

I'm 100% sure it's the correct voltage and wattage.

Checking directly from the battery is a good idea. I shall do that and post the results.

[Matt Freeman]

Tested.
The bulb is really bright straight off the battery, I checked both filaments and they're perfect.

So, then I put the bulb back into the headlamp socket and ran the engine. I ran a wire directly from the earth of the bulb to the engine case hoping that this would demonstrate a bright bulb showing me that the problem is a bad earth but unfortunately it didn't. With the earth testing wire the bulb was still dim.

So, the current is being zapped on it's way to the bulb wiring in the headlamp, something is pulling current from that circuit or shorting somewhere.

Any ideas on what to check next?
Thanks again.

[69chris]

crappy, dirty connections in the light switch itself ??

[bypass2]

maybe the bulb holder/ socket faulty

[Islander]

Check the wiring methodically from the lampholder back to the battery via the switch. It's more likely to be a corroded or dirty connection/contact than a short.

[smegballs]

[Matt Freeman]

[Matt Freeman]

[smegballs]

[misscrabstick]

The headlamp runs from the generator and not the battery, the question is is the magneto kicking out enough volts to power the headlamp? if it is then where are the volts going before they get to the headlamp, with the engine running locate ( using wiring diagrams) the wire that powers the headlamp circuit and measure the output with a volt meter, if it is good then you need to go through the headlamp circuit methodically until you locate the issue, that means measuring the volts at various places on the way from the generator to the headlamp bulb.

I remember from my 6 volt days on a Yamaha FS1E how totally hopeless the lighting is, I had to ride dark country lanes on my to and from college and preyed for a slow moving car to be in front of me so I could see the way, 6 volt electrics are shit by design and any brightness only comes with a lot of engine revs.

[Matt Freeman]

SOLVED.
This is a weird one.
The problem seems to be this little component that I noticed was a non original addition to the electrical system. It's the lower of the boxes in this photo.

https://i1138.photobucket.com/albums/n528/handmadematt/92765903-1df0-4014-9552-fb7bfe308ecb_zps09a21492.jpg

I had a hunch that it was non origional becasue the singe red wire that somes from it was not harnessed in any of the looms and ran a strange course back under the seat. It is also not shown in any of the photos of this area in the original workshop manual that I have. You can only see the limiter and the CDI.

It was wired to the diode rectifier that is for the battery charging. Which incidentally in the wiring diagram only has two connections and not this erroneous third. Again confirming that this is non original.

Simply by disconnecting this wire the headlamp lights properly. (It's till pants but it is properly.)

Everything else seems to work fine still so I think I'm just going to remove it and get on with my life.
Any thoughts? Why was it added? What is it?

[Nobby the Bastard]

Looks like it's a ballast resistor. It's supposed to drain excess charge when the lights are turned off.

It should be a higher reistance that the lighting circuit. That way, the electricity takes the easiest path (i.e. through the lights) when the lights are turned on.
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Triumph Sprint ST 1050

[Matt Freeman]

That makes sense.
What will the problem be with removing it then?
Should I check the voltage at the battery with the engine running and the lights off to make sure that it isn't getting overcharged?

The previous owner said that he had the magneto coil re-wound.
Is that relevant? (Perhaps the newly wound magneto has excessive power and therefore this was fitted to prevent overcharge and there was no thought to how it would effect the lights?

Everyones thoughts are welcome.
Thanks.

[misscrabstick]

I am not sure but I will take a guess as some sort of voltage spike absorber when switching from low to high beam or the other way, stops bulbs blowing?

Any numbers on it? tried googling them?

[Nobby the Bastard]

I've done a bit of checking and if it's a ballast resistor, it might be there to protect the ignition coil from excess current.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Islander]

Check the resistance value against the manufacturer's specification - it'll be a wirewound resistor and they can develop shorted turns the same as any coil.

[Vincent]

Has the bike been converted to electronic ignition or is that original?

If the set up is like my '77 125, they sometimes have problems with coils in the magneto breaking down. Look in the manual for how to test them with a multi meter. If it is one of the coils, they can still be had fairly cheap, there's usually one or two on eBay USA.
____________________
Space Is Deep

[Matt Freeman]

[Matt Freeman]