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K100-forum.com » Technical, repair and troubleshooting » Starter relay gone.. twice

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1Back to top Go down   Starter relay gone.. twice Empty Starter relay gone.. twice Sat Apr 08, 2023 8:28 pm

Gast1y

Gast1y
active member
active member
Hello,

I hope you are having a great holiday.

So was I with my beloved k100 and this happened. First occasion with this issue was straight after winter where I had a short somewhere and my starter kept turning without the key/emergency switch turned off. Battery went dead and the starter stopped turning. I thought perhaps the low voltage battery caused it, so I charged it. As soon as I added my ground to the frame, sparks everywhere. Starter kept turning and the starter relay was blown.

I replaced it, it was all good for 700km and two days. This time I got my bike fired up, noticed no lights. Thought I will turn off and on the bike. Starter kept turning again.... I could still ride, no problem but lights went off and could not do any turn signals what so ever. It went glitching out, as in, I would use the right signal and both would come on and not in a  constant pace. Faster, slower, both, then just left etc. Crazy. only way to stop it is to disconnect the battery, when I plug the ground back in, sparks everywhere.. fireworks haha..

Previously, when first encountered this starter issue, I did not check if my lights were going crazy the first time, it was just a melted starter relay. I replaced it, then it was all good.. for 700km and two days again..

Any troubleshooting tips? Noticed my low beams never worked. Could that be the case, I doubt it..

    

2Back to top Go down   Starter relay gone.. twice Empty starter relay gone Sun Apr 09, 2023 12:18 am

daveyson

daveyson
Life time member
Life time member
You maybe have two problems, a poor earth in the starting circuit, and an intermittent short, but dunno how bad the spark problem was.

With a good, well charged battery connected and ignition off, connect a test light to battery positive. Now touch the probe to the gear box casing, the test light should glow. Then touch the probe to the starter motor terminal. If it doesn't glow, you want to dismantle the starter, clean it, and check the brushes for length. If it smells like burnt plastic, its toast, replace it.

If the spark isn't really much, and removing one of the fuses stops it, that might isolate the problem. If the spark problem only happens for example with the handlebar on full lock, the short might be in the key and kill switch part of the circuit, the key might even have got hot. It kept turning until the battery went dead, hopefully just some wiring insulation melted and you only have to replace some wiring. The wires to battery positive, one of them may show signs of heat damage, or may get hot while cranking. It would be good to use a circuit breaker while trying to isolate the problem. You could install it permanently on the bike afterwards, that could prevent your bike from catching on fire in case a short occurred while you are riding. In the how-to section of this forum is a thread called "Quick fix, circuit breaker, save your brick from burning" with more details.


__________________________________________________
11/1985 BMW K100RT (late model)  Vin. 0090567
 ~120,000 km
    

3Back to top Go down   Starter relay gone.. twice Empty Re: Starter relay gone.. twice Sun Apr 09, 2023 1:35 am

duck

duck
Life time member
Life time member
Did you replace it with the same OEM relay or a different relay?


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

4Back to top Go down   Starter relay gone.. twice Empty Re: Starter relay gone.. twice Sun Apr 09, 2023 8:42 am

firstle

firstle
Life time member
Life time member
earthing problem , i have noticed on my ex police model the standard earth is doubled up and it has a extra large strap type earth from yokes to frame at the front ? i have not seen this before but maybe a good idea , some one here will know why they did this .

    

5Back to top Go down   Starter relay gone.. twice Empty Re: Starter relay gone.. twice Sun Apr 09, 2023 10:59 am

Gast1y

Gast1y
active member
active member
duck wrote:Did you replace it with the same OEM relay or a different relay?
Replaced with the OEM bosch, but I suspect that the battery is weak and thus can be the cause of the problem.

    

6Back to top Go down   Starter relay gone.. twice Empty Starter still runs Sun Apr 09, 2023 6:28 pm

Kr4mo

Kr4mo
active member
active member
Gast1yThe lights are not coming on because the load *(lights) relay is grounded thru the positive post of the starter, so if it's running there's no ground for the relay and no lights.  Starter relay sticking is the result of excessive current draw at the starter or a weak battery causing the contacts to weld.  Rebuild your starter, add some grounds to the frame and engine and charge up or replace your battery. wrote:Hello,

I hope you are having a great holiday.

So was I with my beloved k100 and this happened. First occasion with this issue was straight after winter where I had a short somewhere and my starter kept turning without the key/emergency switch turned off. Battery went dead and the starter stopped turning. I thought perhaps the low voltage battery caused it, so I charged it. As soon as I added my ground to the frame, sparks everywhere. Starter kept turning and the starter relay was blown.

I replaced it, it was all good for 700km and two days. This time I got my bike fired up, noticed no lights. Thought I will turn off and on the bike. Starter kept turning again.... I could still ride, no problem but lights went off and could not do any turn signals what so ever. It went glitching out, as in, I would use the right signal and both would come on and not in a  constant pace. Faster, slower, both, then just left etc. Crazy. only way to stop it is to disconnect the battery, when I plug the ground back in, sparks everywhere.. fireworks haha..

Previously, when first encountered this starter issue, I did not check if my lights were going crazy the first time, it was just a melted starter relay. I replaced it, then it was all good.. for 700km and two days again..

Any troubleshooting tips? Noticed my low beams never worked. Could that be the case, I doubt it..

    

7Back to top Go down   Starter relay gone.. twice Empty Re: Starter relay gone.. twice Sun Apr 09, 2023 8:17 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
How much cranking does the engine need to start? 

How long does the battery crank the engine before it runs down enough to weld the contacts?

Are you sure the alternator is charging the battery when the engine is running? 

These engines normally start in a second or less.  If you are cranking long enough to run the battery down and weld the starter relay that is the problem you need to address first, right along with finding out why the battery is running down so quickly.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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