electrical problem - 1980 Sportster
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6th Gear
Joined: Aug 2017
Posts: 10
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From: Ohio
electrical problem - 1980 Sportster
My battery has started dying out. I checked and the battery is ok. I did the voltage check and I'm at 12.5 with the engine running and revved. I read these forums and thought the regulator might be the problem. I checked and a prior owner wired in an old Bosch mechanical regulator (instead of the solid state that came with that model). So I swapped out Bosch for Bosch. Didn't fix it. So then I took the generator apart. It was dirty. I cleaned the copper part, but maybe only halfway (doesn't look like a brand new penny). And my brushes are right at 1/2 inch or maybe a touch more. Put it all back together and I'm still at 12.5. And I will say my generator makes some noise, but I've read here that's ok. Any ideas? Thank you.
Cruiser
Joined: Jun 2015
Posts: 203
Likes: 50
From: Orlando, Florida
Don't know about an Ironhead, but my '86 was eating batteries. First one, I figured it was used up and shot. Got a new one and it lasted a month or so. Got it's replacement, then started monkeying around. Wound up it was the insulation on the wires from the stator behind the clutch basket where they came out from behind the primary were cracked or missing from oil and road crud, shorting out intermittently as far as I could determine. I replaced the stator, but I probably could've gotten by with a good cleaning of the wires and using some liquid insulation goop on them.
Here is a simple load test:
1. fully charge the battery
2. Disconnect the spark plug leads and lay them on the cylinder heads so that they are grounded. Make sure that they stay there during step 4
3. Attach voltmeter leads to the battery terminals.
4. Watch the voltmeter DC volts reading while cranking the engine for 10 full seconds, no more
If the reading goes below 10 volts [some say 10.5 ] the battery has failed the load test and needs to be replaced. [The electrical system of the bike needs more that 10 volts to start the engine].
To be good the battery needs to be able to [1]take a charge, [2] hold that charge during starting, and [3] hold that charge over a long period of time.
Last edited by IronMick; Aug 19, 2017 at 07:39 PM. Reason: corrected amps to volts :)
Seasoned HDF Member
Joined: May 2008
Posts: 21,129
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From: South Carolina
With the engine rev'd up you should get 13 to 14.
4. Watch the voltmeter reading while cranking the engine for 10 full seconds, no more
If the reading goes below 10 amps [some say 10.5 ] the battery has failed the load test and needs to be replaced. [The electrical system of the bike needs more that 10 amps to start the engine].
To be good the battery needs to be able to [1]take a charge, [2] hold that charge during starting, and [3] hold that charge over a long period of time.
4. Watch the voltmeter reading while cranking the engine for 10 full seconds, no more
If the reading goes below 10 amps [some say 10.5 ] the battery has failed the load test and needs to be replaced. [The electrical system of the bike needs more that 10 amps to start the engine].
To be good the battery needs to be able to [1]take a charge, [2] hold that charge during starting, and [3] hold that charge over a long period of time.
Tourer
Joined: Mar 2009
Posts: 410
Likes: 127
From: Iowa
It sounds like you don't have a factory service manual for your bike, or you'd have done the generator output test.
From the manual:
1. Remove both "A" and "F" terminal wires
2. Adjust voltmeter to read on a 10 volt DC scale
3. Connect positive voltmeter lead to the "A" terminal and the negative lead to ground.
4. Start motorcycle and run at 2000 rpm. Voltmeter should read a minimum of 2 to 2.5 volts.
If correct voltage is read, generator is in good condition.
If zero or very little voltage is read, polarize the generator and repeat the test.
If after polarizing the generator no voltage is read, disassembly and repair will be required.
If your genny brushes are only 1/2 inch long, they're right at the threshold of needing to be replaced. (also per the manual.)
The factory service manual and parts manual are pretty much required if you're going to work on your own bike.
From the manual:
1. Remove both "A" and "F" terminal wires
2. Adjust voltmeter to read on a 10 volt DC scale
3. Connect positive voltmeter lead to the "A" terminal and the negative lead to ground.
4. Start motorcycle and run at 2000 rpm. Voltmeter should read a minimum of 2 to 2.5 volts.
If correct voltage is read, generator is in good condition.
If zero or very little voltage is read, polarize the generator and repeat the test.
If after polarizing the generator no voltage is read, disassembly and repair will be required.
If your genny brushes are only 1/2 inch long, they're right at the threshold of needing to be replaced. (also per the manual.)
The factory service manual and parts manual are pretty much required if you're going to work on your own bike.
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