General > General Technical Chat
Motorcycle Electrical Issues
floobydust:
It's an extra half-wave load so I suspect this thing is phased, it seems odd. So the new bridge could be wired flipped on the AC terminals?
OP has two problems - the ignition system , and the charging system with the new bridge rectifier which seems to run hot.
The bike should be able to run entirely off the battery, towards troubleshooting the ignition system issues. I wonder how you set dwell and timing, a timing light could also reveal if the points are working and stable.
Dundarave:
I found this Matchless manual that might help with the repairs:
http://archives.jampot.dk/book/Workshop_manuals/1957-1964__=M=_Workshop_Instruction_Manual_all_models_SEARCHABLE.pdf
In the electrical section, it explains how the alternator coils are “doubled up” in the “emergency” ignition mode, the purpose being to charge a dead battery enough to run properly. It warns to only leave it in this position for 10 minutes, just enough to give the battery minimal charge.
mendip_discovery:
Today the delivery person brought me some goodies and so I fitted a new battery and a new rectifier.
Turns out you are all wrong, and so was I :-)
It was the damned fuel taps, they were dribbling like Dave going for a pee. So gave them a quick reverse blow and there was a little more flow. Took it up the road and woop the thing flies again. Thoughts are that when we opened the throttle they were preventing even the fuel in the carb from flowing as there was a blockage at the tank.
So I will run the fuel down a bit and then see if I have the confidence to remove the old taps to give the filters a clean and the tank a good flushing. That damned Ethanol.
The bike has an emergency mode and it will never happily run on it, it will start and ride but it is not great fun to ride. I was trying to start it in normal mode so it should have been just fine.
--- Quote from: Circlotron on May 09, 2023, 03:22:27 am ---If you can reach it, while the engine is idling, remove the plug wire and see how far the spark will jump while idling. Using that as a gauge, slowly increase the revs and see if the spark fizzes out or begins to fire erratically.
--- End quote ---
Do I look that daft! That is a surefire way to get the output of the coil running via you. Next time you see a friend starting a bike, take the plug out, and then put it in the cap, ask them to try and start it and see how long you can hold on. My dad got a V8s worth at the weekend, he is still muttering about it now.
--- Quote from: Circlotron on May 09, 2023, 05:51:15 am ---
--- Quote from: Dundarave on May 09, 2023, 04:41:10 am ---I had a 1972 Triumph Trident many years ago, and discovered that while it would run without the battery, it needed a decent-sized capacitor (I used a 2200uF electrolytic) in order to smooth out the pulsating DC current.
I think what happens as the revs start to rise, the pulses (with no battery to smooth them out) don’t allow the coils to work properly.
Try putting a big cap across the battery connections and give it a try.
--- End quote ---
I was thinking similar, but you would expect the rectified pulses from the alternator would always have the same phase relationship to the ignition points, so a pulse would be available while the points are closed and the coil is charging. Unless of course there is a mechanical advance mechanism on the points and as the engine speeds up it moves the points closed position too far away from the alternator DC pulse and so it begins to run badly?
--- End quote ---
This bike was the epitome of modern tech, gone was the manual advance and retard system that was good for giving you a broken ankle if left in advanced. It has a auto-advance/retard which is just some weights and some springs that as soon as the engine spins they move out. The next advance was electronic ignition but that came after this firm was out of action, which is a shame as the AJS/Matchless brand was the creator of the suspension systems most use today.
--- Quote from: Dundarave on May 09, 2023, 04:41:10 am ---I had a 1972 Triumph Trident many years ago, and discovered that while it would run without the battery, it needed a decent-sized capacitor (I used a 2200uF electrolytic) in order to smooth out the pulsating DC current.
I think what happens as the revs start to rise, the pulses (with no battery to smooth them out) don’t allow the coils to work properly.
Try putting a big cap across the battery connections and give it a try.
--- End quote ---
I might still try this as the battery is ok but I did notice the rectifier isn't perfect and might help a little to have a bit of buffer.
Attached below is the wiring diagram I made up when I made the new loom. I upgraded the wire to 2mm² and added an extra positive earth from the headlight to the frame as it's 6V electrics so v-drop is always a worry and the use of the lights after dark is akin to using a candle. I was also a sad person for replacing the wire with the same colour markings as the original loom as I wanted the next owner to be able to read the manuals and make sense of the connections. Nothing worse than a vehicle wired up with just blue wire, how would you know which wire to cut?
EDIT: It is a single-phase stator.
floobydust:
--- Quote from: mendip_discovery on May 10, 2023, 08:09:24 pm ---[...] Turns out you are all wrong, and so was I :-)
It was the damned fuel taps, they were dribbling like Dave going for a pee. [...]
--- End quote ---
Thread is titled "motorcycle electrical issues" and we all believed it :-/O
The wiring diagram still looks weird, why are both AC legs (GB & GW) going to the lighting switch? Not that the switch is decipherable lol.
mendip_discovery:
I thought it was a fuel issue but peer pressure said it was electrical and I had done the carb etc at the weekend so I was left with the magic that is Lucas (the Prince of Darkness) electrics.
A headlight bulb doesn't care is its ac or dc so happy for some of the power to head there. I am sure to get the bike to start I had to deviate from this diagram in a few places but that is just the way these bikes were made.
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