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1964 Yamaha YA6 no spark


cdn_bobber
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Good Morning, 

I ended up with a 1964 Yamaha YA6 which I have gone through. I went to start and it has no spark. I checked the wiring, changed out the regulator, coil and starter/generator/dynamo. It has lights, signals, horn, brake light which all work, but I can't get a spark. When I pulled the bike apart the white wires (armature circuit) was melted, I fixed that. Otherwise I'm stumped, please help!

Cheers

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Welcome Cdn,

Sounds like you've replaced ALL the key components, so assuming they are all wired correctly and compatible with your bike, I'd be looking at the "kill switch". Now I'm not familiar with the YA6 or have access to the circuit diagram, however, on many bikes of the 60's and 70's they had a dedicated switch to ground the coil and stop the spark,  older bikes, the kill switch was wired through the ignition switch, turning the key to 'off' grounded the same wires. Just because the ignition switch "works", doesn't mean it can't be faulty!!   Like I said the switch will 'ground' the circuit. To test it, you would need to disconnect this wire so the switch can't ground it. (The switch may be faulty and be grounding the wire in any position thereby killing the spark)

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I have an update. I tested the starter button with a circuit tester from the battery and the button (circuit) works. I then jumped the starter directly from the battery to starter (M circuit) and it cranked over, but no spark at the points or spark plug. I then jumped the battery circuit (B) and the common circuit (C) at the ignition switch and the starter button would not work. It almost seems the starting switch within the regulator is not engaging. As previously noted I have replaced the original regulator with a NOS one, but I guess that doesn't mean the starting switch works. Thank you again in advance for any advice / thoughts.

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Thanks for the circuit diagram, that's certainly not an easy diagram to follow, they've come a long way with how there are presented today compared to 1964!!

Nonetheless, with a light bulb you can test quite a bit!

Firstly are you getting a voltage on the LT side of the coil ? (LT low tension)

The starter/dynamo has an orange wire going from it to the LT side of the coil, disconnect it at the coil and put a light bulb to earth, does it light up on turning the engine over?

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Update. I think I have figured it out. After looking at the wiring schematic I thought the only thing that could be stopping it was cranking over / starting is the starting switch located in the voltage regulator. I took the regulator off, cleaned the contacts on the starting switch and reinstalled it. It worked, but no spark. I cleaned the contacts on the points and now I have spark. It wouldn't start, but I think that is a fuel issue. I am off to get some gas. I will update later. Thank you Neo for pointing me in the right direction.

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That's good news , at least you've got a spark. Did it start with new fuel?

You mention 'gas', are you across the other side of the pond?

 

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On 11/17/2022 at 11:41 AM, NE0 said:

That's good news , at least you've got a spark. Did it start with new fuel?

You mention 'gas', are you across the other side of the pond?

 

Yes I am. Located in Vancouver, British Columbia. I got the bike to fire once.. but it seems it's getting flooded. I rebuilt the carb. It's getting spark.. I double checked the timing.. any thoughts would be appreciated. Cheers 

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