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Mikey85

Model 85 Brake Light

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Just recently completed restoration of my model 85 Alpina I purchased new back in 1974. Did a lot of dirt bike riding back in the 70s and 80s before it was put into storage for nearly 25 years. Took a lot of photos as I went along so I could get it back original. Engine fired on the forth kick and runs great. Head light and tail light both work as before, however the brake light doesn't function when operating the rear brake pedal.  Bulbs and brake switch are new and check out using a volt-ohm meter. Have attached a wiring diagram of how my bike is wired. Could someone please review the diagram and see if I have missed something or wired it incorrectly. Any other suggestions for possible solutions would be appreciated also.

Thanks,

Mike 

my bul.jpg

M85-2 001.jpg

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Couple of things to check.

Does the switch work as expected i.e. when it is pulled does the circuit connect?

Attached is a scan of a M91 owners manual wiring diagram which basically is the same as the Alpina.

22a.jpg

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I am not an electrician but I think the brake light switch should have power in on one side, power out the other to the bulb, which then earths through the bulb holder? Your diagram shows the switch earthing directly back to the resistor. I think the green wire from the bulb should go to the switch side that is currently earthed, not to the connector giving you two greens at the switch........... but as I say I am no expert and if the bulb holder is not earthed then I have just talked rubbish, so someone else may be along soon with better advice.

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RC,

Thanks for your response. The wiring diagram you attached is the most legible one I’ve seen so far, thanks.  The brake switch operates as expected; when plunger is depressed the circuit connects and when not depressed it is open.  In looking over the M91 diagram, it appears to match my diagram.  I am starting to suspect there may be a problem with the green wire coming from the magneto.

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6 minutes ago, Mikey85 said:

RC,

 

Thanks for your response. The wiring diagram you attached is the most legible one I’ve seen so far, thanks. 

No problem.  Scanned in high res from the original owners manual we have.

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Mikey - 

This topic cropped up a few days ago - Thumbs up! 's topic Oct. 25 - he posted a schematic/scan from Clymer manual explaining how the stop lamp works :IMG_0570.thumb.JPG.bce083962e8f4672abd11c3fba1ef742.JPG

Remember, the stop lamp is fed via the earth/"ground" side of the LT igntion coil in the magneto (the green wire).

You will see that the stop lamp switch needs to have normally-closed contacts, i.e. contact is made when the rear brake is NOT applied.

Is this the way your new switch operates ?

I'm unclear about the fine detail of the rear lamp itself, as it was missing from  my own Model 85, but the separate bulbs originally specified were a festoon type 6v. 4.5W for the rear lamp and a 12v. 18W bayonet type for the stop lamp.........

Hope this helps..

Edited by lorenzo
clarity

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Thanks Lorenzo for your input. My brake light switch operates as you have described.  Don't believe the wiring diagram is for my Model 85.

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Mikey - 

The wiring diagram is correct for a standard mod. 85 with direct (AC) lighting. I have an original owners handbook; this uses the same diagram exactly. 

Your bike appears to have an original-style rear lamp; what bulbs are you using ?

Edited by lorenzo

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Lorenzo,

I have correct bulbs installed (6V-4.5W and 12V-18W), checked them with meter and they are both OK. I guess what threw me off on the copy of the circuit you sent me was the front brake switch; my bike only has a rear brake switch. I disconnected the green wire from magneto green wire and applied 6v DC power supply to the rear brake circuit and brake light worked when brake pedal was depress. So what does that mean?  Has anyone reviewed my schematic to see if it is correct?

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Mikey - 

The "correct" wiring diagram I referred to was the one posted by rcgods. The schematic I posted was merely to show how the brake light works - one switch/two switch, the principle's the same.

.The earth/"ground" side of the igntion coil (the green wire from the magneto) must go through the brake switch (brake off/not applied) or through the bulb and resistor (brake on), thence to earth. You appear to have bypassed this requirement by earthing the green wire at the terminal block - Brn. wire to "frame grd"., meaning the switch circuit is not working.

Try removing the brown wire............

Lorenzo.

Edited by lorenzo
missing text

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A lot of the Japanese enduro bikes from the 80's and 90's had lighting coils in the stator that could only produce between 20 and 30 watts. Enough to power a headlight and tail light, but not enough for a brake light. To add a brake light we would wire a resistor into the tail light circuit and bypass the resistor with a brake light switch. The bulb would be dim until you hit the brakes. Some would also use the similar method for a hi/low beam headlight using a handlebar mounted switch.

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Lorenzo,

Going to remove the brown wire at the terminal block as you have suggested. I wondered if that might be the problem but remembered it was wired like that before I disassembled the bike.  I'll let you know the results soon.

Thanks,

Mike 

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Lorenzo,

I removed the brown wire and the brake light works now, however both bulbs illuminate bright. Are both bulbs supposed to illuminate when braking?  With the headlight switched on and braking, both bulbs are much dimmer.  That brown wire grounded to the frame has been that way since I bought the bike new in 1974, wonder why.  Feeling better about the wiring except for both bulbs illuminating upon braking. Your thoughts?

Thanks,

Mike

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Lorenzo,

Fixed the issue with both lights illuminating when operating brakes. I had the headlight ground at the same terminal the brown wire was attached to the terminal block opposite the green wires. Removed the brown wire and grounded the headlight wire to the frame and all is working well.  Thanks for your help.

Mike

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Mikey -

I was about to explain that the brake light and rear light bulbs seem to be sharing  a common earth/ground connection...........now we know  why !

I'm happy you have it sorted and glad to be of help.

That's a  nice looking bike, by the way.     I'm presently trying to sort my own Mod. 85 (also a '74), and if it turns out half as well as yours I'd be quite satisfied.

Happy trail riding,

Lorenzo

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