Author Topic: Ground wires from battery  (Read 2162 times)

Offline foliver

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Ground wires from battery
« on: February 12, 2024, 03:34:25 PM »
Hello all.
k75C 1986

My bike has just one cable from the - of the battery to the gearbox ground point.
It's not a big one, a little "thin" one as i perceive it.

The point is that i've had issues with the starter relay in the past ( and yesterday), because of low voltage in the battery.

I need to say that even if i don't use the bike a lot, i charge it time to times, and the battery is one year old.
As yesterday the relay stucks again, and i was in need to turn off the bike releasing the clutch in 1st gear and full brake, today i've pluged in a new Battery tender junior 800 ( https://www.batterytender.com/battery-tender-12v-800ma-selectable-lead-acid-lithium-battery-charger_7) to keep it allways charged, and the battery tender in 10 minutes shows green, as a full charged battery.....

So my mind deduces:
1. The battery is not good anymore, and doesn't has "amperes to deliver"
2. The starter ( 1 year old) despite having polished the internal contacts the first times it get's stucked, now it's "sensible to low voltage"
3. The Starter is not receiving good voltage because of the thin wire and where it's connected ( i sanded all the ground points one year ago, and applied deoxit)

It's silly to think that the wiring is not the best, and if the battery drops a little in voltage the starter get stucked straight?
A healthier ground to the starter, can be of help in that way?

Or i'm delirious?

Last info: 2 days ago, after a while without riding i've seen in the negative contact of the batterie itself, a white formation, that i was abble to clean with a screwdriver, but maybe this generates more resistance to the voltage, i think on clean that with isopropil alcohol.

PD: i don't have any extra instruments plugged in the battery.




  • Montevideo, Uruguay
  • Bmw K75C 86

Offline frankenduck

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Re: Ground wires from battery
« Reply #1 on: February 12, 2024, 03:53:39 PM »
Even though BMW did upgrade the ground cable it should still start fine with the skinny ground cable.




You can take the battery to an auto parts store and they will "load test" if for free.
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Offline foliver

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Re: Ground wires from battery
« Reply #2 on: February 12, 2024, 07:07:47 PM »
Thanks Frankenduckm yes, mine is the old one.
The only ground cable that connects to the batery is that one? my bike has just this one
txs!
  • Montevideo, Uruguay
  • Bmw K75C 86

Offline frankenduck

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Re: Ground wires from battery
« Reply #3 on: February 12, 2024, 07:16:13 PM »
Yes, it grounds to the transmission only and then current flows through to the frame via the bolt at the top of the bellhousing.
Once I had a Collie pup. Dug a hole and covered him up. Now I sit there by the hour. Waiting for a Collie-flower.
New to K bikes? Click here.
K Bike Maintenance & Mods: Click here.
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Offline Laitch

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Re: Ground wires from battery
« Reply #4 on: February 12, 2024, 07:42:07 PM »
Remove the cable from the transmission. Clean the transmission mounting point and the cable terminal with a wire brush or wheel until all contact surfaces with each other are smooth then bolt them up then see if there is a difference.
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  • 1995 K75 89,000 miles

Offline foliver

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Re: Ground wires from battery
« Reply #5 on: February 12, 2024, 08:14:16 PM »
Txs both.
I was checking with the multimeter votage on the bolt, and on other parts of the frame ant there's the same.
Current seems to flow ok. Even in the clutch handle i find the same voltage than in the transmission bolt.
Anyway, i'll clean both battery terminals, and transmission bolt again.
I've a Battery Master Disconnect Cut Off Switch since 2 years, uninstalled, may be is the moment to do all at the same time, along with the fast battery tender connector....
  • Montevideo, Uruguay
  • Bmw K75C 86

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