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Mechanical and Technical Mechanical and technical topics, help, and discussions

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May 20th 2018, 04:08 PM   #1
 curve addict's Avatar
 
  Apr 2016
  Des Moines, WA

  ...1987 Yamaha FZR1000...
Old bikes woes and repairs, two-wire type alternators.

Does your old bike run good, but seems to cook batteries and pop light bulbs? Is it charging within the normal range of 13.5VDC and 15.5VDC, but on the high side? Can you solder wires and such? There may be a fairly simple and inexpensive fix for your problems.

Most modern, newer, motorcycles run alternators with permanent magnets. I'm not talking about those. I'm talking about the other ones; the ones that run with electromagnets, use brushes and use an exciter voltage, usually from a small-gauge wire, which energizes the rotor to develop the required magnetic field. The heavier-gauge wire feeds the battery.

This one bike in question happens to be a 1987 Yamaha FZR1000T, but variations of this same style of alternator exist in many older machines and some of the newer machines that run high capacity, air-cooled units. After repairing an issue inside my alternator, I noticed that, after a couple of short runs, the charging voltage had reached 14.8+VDC. It had been lower. This is within spec, but the higher voltage creates more heat in the electrical system then necessary, worst during long runs, and will reduce the lifespan of many components, especially the battery. I'm a curious sort, and have some experience with electrical systems, so here's what I discovered. The first part is how I found the problem:

Edit: I took the photos after the fact, just so ya know.
Attached Thumbnails
Old bikes woes and repairs, two-wire type alternators.-1.1-2wire_alternator-relay-fix.jpg   Old bikes woes and repairs, two-wire type alternators.-1.2-2wire_alternator-relay-fix.jpg  
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Edited by curve addict on May 20th 2018 at 04:40 PM Reason: adding information
May 20th 2018, 04:15 PM   #2
 curve addict's Avatar
 
  Apr 2016
  Des Moines, WA

  ...1987 Yamaha FZR1000...
A quick look at the wiring diagram shows, and here's the problem, that about 5 feet of wire, 6 friction connections (at plugs), one 30A fuse holder (with 4 more friction connections), 12 crimp connections (only two are soldered from the factory) and one switch lay between the battery and the terminal at the alternator. It also shows that the same wires that lead to this spot power practically everything else first, then eventually make it to the alternator. Add some tarnish between the wires and the crimp connections, and the friction connections, and the wiring harness drops almost 0.9 volts from heat loss. The alternator senses that it's not making enough electricity, so it works harder than it has to. At the same time, it's overcharging the battery and overworking the vehicle's electrical system. 14.8VDC isn't devastating, but it does heat things up more than necessary.

The next thing that I did was to replace and solder all of of the friction connectors and solder each remaining crimp connection that was not buried in the harness wrapping. I used these; perfect-fit replacements for the original. I applied dielectric grease to all of the friction connections. Next test; the voltage drop improved from 0.88VDC to 0.58VDC. It was a significant improvement, but I had hoped for more. A shorter path, one that wasn't feeding the entire bike, was needed.
Attached Thumbnails
Old bikes woes and repairs, two-wire type alternators.-terminal-pin-34-8967.jpg   Old bikes woes and repairs, two-wire type alternators.-terminal-pin-34-8968.jpg   Old bikes woes and repairs, two-wire type alternators.-1.3-2wire_alternator-relay-fix.jpg   Old bikes woes and repairs, two-wire type alternators.-1.4-2wire_alternator-relay-fix.jpg   Old bikes woes and repairs, two-wire type alternators.-1.5-2wire_alternator-relay-fix.jpg  

Old bikes woes and repairs, two-wire type alternators.-1.6.jpg  
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Edited by curve addict on May 20th 2018 at 05:47 PM Reason: adding photos & spelling fixes
May 20th 2018, 04:20 PM   #3
 curve addict's Avatar
 
  Apr 2016
  Des Moines, WA

  ...1987 Yamaha FZR1000...
more:
Attached Thumbnails
Old bikes woes and repairs, two-wire type alternators.-1.7.jpg   Old bikes woes and repairs, two-wire type alternators.-1.8.jpg   Old bikes woes and repairs, two-wire type alternators.-2.0.jpg   Old bikes woes and repairs, two-wire type alternators.-2.3.jpg   Old bikes woes and repairs, two-wire type alternators.-2.4.jpg  

Old bikes woes and repairs, two-wire type alternators.-2.5.jpg  

Edited by curve addict on May 20th 2018 at 05:04 PM
May 20th 2018, 04:25 PM   #4
 curve addict's Avatar
 
  Apr 2016
  Des Moines, WA

  ...1987 Yamaha FZR1000...
I almost forgot; you need to connect the 85 (or 86, whichever terminal you haven't used yet) to a good ground. The end result: Only a 0.05VDC drop from battery to the field exciter terminal on the alternator and a very steady, 14.4VDC charge at the battery during all testing thereafter.

Maybe this will help a few of you out there.
Attached Thumbnails
Old bikes woes and repairs, two-wire type alternators.-2.6.jpg  

Edited by curve addict on May 20th 2018 at 05:10 PM Reason: adding information
May 20th 2018, 05:43 PM   #5
 FeralRdr's Avatar
 
  Jan 2016
  Adjacent to the Hobbit Garage

Splendid Job Dave.

Now take it for a nice test ride; preferably someplace interesting.
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May 20th 2018, 06:17 PM   #6
 curve addict's Avatar
 
  Apr 2016
  Des Moines, WA

  ...1987 Yamaha FZR1000...
Good plan. To finish, I just need to fabricate a mounting bracket for the voltmeter and plug that sucker in.
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May 21st 2018, 07:28 AM   #7
 FeralRdr's Avatar
 
  Jan 2016
  Adjacent to the Hobbit Garage

Quote:
Originally Posted by curve addict
Good plan. To finish, I just need to fabricate a mounting bracket for the voltmeter and plug that sucker in.
Just use some LEGO's Dave.


Everyone loves LEGO's.

And... That'll get you back on the road for a nice test ride.
May 21st 2018, 08:15 AM   #8
 Nathan's Avatar
 
  Jan 2016
  space needle

nice writeup!

Quote:
Originally Posted by curve addict
Good plan. To finish, I just need to fabricate a mounting bracket for the voltmeter and plug that sucker in.
been thinking about getting one of these https://www.gearbest.com/other-motor...pp_364140.html

May 21st 2018, 08:07 PM   #9
 Brassneck's Avatar
 
  Apr 2016
  Seattle, WA

  '79 XS650; '01 FZ1
Great job with detailing the steps. This is a good idea, especially for us guys running 30-40 yr old bikes (And quite a lot cheaper than converting over to a PMA system).
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