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Discussion Starter · #1 ·
Greetings everyone,

After a long December work month of 70-80 hour weeks and no riding, I had the time to finally get the bike on the road. With the hours I was working and the nature of my work it made sense to use the car rather than the bike. I put the keys in, turned and saw all the lights flash on, turned off the kill switch and when I pressed the button that would grant me pure happiness (starter), I heard a click and lost all power. Off to get the tool box then..

I have a 1980 CM400A. My first initial thought was a fuse, and when I checked the main 15A fuse one side was starting to corrode and was loose. I replaced it but no power, so thinking I may have a dead/low battery I let it charge for about 5 days. Today I cleaned the cable connections and installed the battery and still no power. I grabbed my multimeter and began testing everything, starting from the battery on. Everything was getting power until I hit the rectifier/regulator (original). Power is going into the unit but nothing is coming out, thus nothing after that point has power. I checked and cleaned the connections that connect to the unit, which weren't bad at all, but still no power. I checked and cleaned the ground, using it as my ground for my meter, but still no power.

My theory is that when I hit the starter, the corroding main fuse failed to do it's job and potentially fried the unit, or maybe it just decided to give me the bird and fail. To my understanding the unit converts DC into AC so the systems on the bike can work correctly, so if the unit is toast it'd make since that nothing is working. I know only the very basics of electronics and electricity, so I wouldn't be surprised if I missed something or am wrong.

Any advice? If the rectifier/regulator is bad, does anyone have a source to replace it?

Thanks,
David

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Hook your multimeter up to the battery, dcv mode.
What does it read?
Now turn the bike on and press the starter button.
What does the multimeter read?
 

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Discussion Starter · #3 ·
In DCV mode, set at 20:

With bike turned off: Battery reads at 0.5 +/-
With bike turned on: Battery reads at 12.85
With bike turned on with starter button pressed: Batter reads at 12.85
 

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Did you replace the main fuse?
Are you getting voltage on both sides of the fuse?
You're supposed to be measuring battery voltage at the battery terminals. Should read different voltage with bike off than on.
 

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Discussion Starter · #5 ·
I replaced the main 15A fuse with a new 15A fuse, and tested both sides of the fuses on the front and back, where the wires run to and from the fuse box. I got power from the whole box, all sides. I did these tests, all the tests of the electrical system, with the bike on to confirm where power was at.
 

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Maybe your starter button is dirty or your solenoid is bad. Your battery might be bad too, but hard to tell.
 

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Discussion Starter · #7 ·
The battery is about 2 years old, but you never know. When I say that the bike has no power with the key on I mean NO POWER haha, no lights, horn, nothing. That's why I think maybe the rectifier/regulator is bad as the bike isn't getting the proper current.
 

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The regulator has nothing to do with the start circuit. The Red wire from it will show power from the battery BUT the wire is supplying charge voltage to the battery when running.
Follow the Red wire from the battery to the fuse block and forward to the ignition switch, that's the primary power circuit
 

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Did you load test the battery? no-load open circuit voltage doesn't mean much. Put your tester leads on the battery posts and hit the starter button. Still 12 plus volts? With the scale still set on volts, put one lead on the cylinder head and the other lead on battery minus post. If the circuit is good, the meter should read less than one volt under load. Test the positive side the same way, one lead to the battery post and the other lead to the fuses. A reading of 12 volts between the battery and the fusebox would indicate a problem there. A high reading between the main fuse and the ignition/lighting fuses would point to a problem in the main switch or the wiring connectors between them.
 

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Discussion Starter · #10 ·
What exactly is the ignition switch? Again I'm not well versed in electronics and some of the electronic parts on the bike.

Also, I think I entered the wrong data about the battery, and noticed something that I think is worth mentioning:
With the key turned OFF, the DCV meter read 12.85V, with the test tips on the battery terminal. Turning the key ON, the voltage dropped to about .19V, then gradually climbed to a max of just over 2V, then went down to stay around .75V. Hitting the starter with the key on did not change the voltage.

I did follow the red wires, that comes from the battery, to the fuse box and to the rectifier. Readings were .9V+/-. I could not find power after the rectifier, and in the general area where the blinker solenoid is. The object under the fuse box, that is surrounded by rubber and has a clip connector on the top and a regular easy-pull-off connector on the bottom, has power in the clip connector (red wires) but nothing coming out of the other connector. Hopefully this helps.
 

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"What exactly is the ignition switch?" , the main switch(where you put the key).
" Turning the key ON, the voltage dropped to about .19V", sounds like the battery is toast. Try a different battery, in a pinch you could jump it off a car battery.
 

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You have a dead battery.
Plates hold a 'surface charge' when not under load but all cells seem to be toasted to overdone. Leaving charger on for 5 days didn't help, a timer switching on and off is better. Is battery boiled dry?
You bike has 'self generating' ignition system so jump starting from a car battery will allow you to get it running and ceck things if you really want to?
Except for the low speed ignition charge/trigger coil I've found electrical system is the most reliable part of CM/CB 3 valve range.
Don't have car running when jump staring as 100~ 150 amp car alternator could cause bike battery to explode
 

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Discussion Starter · #13 ·
So indeed the battery is bad. I took crazypj's advice and attached cables from the car to the bike and behold, lights and starting action! Got a new battery ordered from the local bike shop along with a new tire. Thanks for all the help guys, you all are amazing as usual!
 
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