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K100-forum.com » Technical, repair and troubleshooting » Electrical » Will low battery voltage disallow a start?

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SniperX

SniperX
Silver member
Silver member
My battery works well enough to spin the starter, a d bike MAY or may not start for a few seconds....but after it does and won't restart till you fully charge the battery then dies again. I seem to have read somewhere this is a sign your battery is in need of replacement t because the computer won't allow the bike to run in an under voltage situation.

    

duck

duck
Life time member
Life time member
Take your battery to an auto parts store and ask them to "load test" it. It's free.


__________________________________________________
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
    

SniperX

SniperX
Silver member
Silver member
So do k bikes really do this when the battery starts to go belly up?


__________________________________________________
1985 BMW K100RT, 2006 Ducati ST3, 1996 Honda CBR1000f, 2001 Honda XR400r
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Not that I have ever heard.

A bad battery may give you a start, but if the alternator doesn't start pumping out the amperes the engine won't run long, and you'll suck enough power out that you won't get another start out of it.

Get you battery load tested and then check the alternator for 13.8 volts when the engine is running.  You may have a bad voltage regulator/brushes in the alternator that isn't charging the battery properly and allowing it to run down.


__________________________________________________
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
    

Rick G

Rick G
admin
admin
There is nothing built into the computer system to prevent the bike operating if the battery is bad but it is that the computer itself wont work if the voltage is below 9.5 volts. However if the battery is in such bad shape that the computer wont work then it is highly unlikely the starter will turn the engine.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1999 K1100 LT with a Big Block 1200
    

rfw

avatar
active member
active member
WARNING!

With all variations of the K100, attempting to start the engine with a low (or marginally low) battery will will result in excess current being drawn, and the starter relay's contacts welding together. When that happens the result is that the starter will endlessly crank (slower and slower!). The only way to stop it is the disconnect one of the battery cables.

Bob.

    

duck

duck
Life time member
Life time member
rfw wrote:WARNING!

With all variations of the K100, attempting to start the engine with a low (or marginally low) battery will will result in excess current being drawn, and the starter relay's contacts welding together. When that happens the result is that the starter will endlessly crank (slower and slower!). The only way to stop it is the disconnect one of the battery cables.

Bob.

This starter relay sticking MIGHT happen. I've tried to start numerous K bikes with very low batteries over the years and I've never had a single starter relay stick on me. I'm not denying that it CAN happen but in my experience it's not as much of a predestined outcome as some would have you believe.


__________________________________________________
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
    

rfw

avatar
active member
active member
duck wrote:
rfw wrote:WARNING!

With all variations of the K100, attempting to start the engine with a low (or marginally low) battery will will result in excess current being drawn, and the starter relay's contacts welding together. When that happens the result is that the starter will endlessly crank (slower and slower!). The only way to stop it is the disconnect one of the battery cables.

Bob.

This starter relay sticking MIGHT happen. I've tried to start numerous K bikes with very low batteries over the years and I've never had a single starter relay stick on me. I'm not denying that it CAN happen but in my experience it's not as much of a predestined outcome as some would have you believe.

You are right... low battery voltage MAY cause relay contacts to weld, but not always. But it happens relatively often, THis happened to me years ago with my K100RT.

Note that later model K-bikes have a much "beefier" starter relay that seems to have eliminated the problem.

Bob

    

Matthew-Brisbane

Matthew-Brisbane
Life time member
Life time member
I had a starter relay  weld shut on me once 
This was before I even  knew it was a thing 

I remember the sicking feeling trying to stop the bike from turning over  


I cant tell you the following 
Ripping the keys out dose not work  
Ripping the fuses out dose not work

Had to grab an allen key and disconnect the earth at the gearbox


__________________________________________________
1986 K100 RS Motorsport
1988 K100 RS SE
1990 K1 known as Barn Find 
2004 F650 GS known as DACK-DACK
 
#### K100 RS Project 
2011 R1200 GS known as Big Blue 
    

Laitch

Laitch
Life time member
Life time member
duck wrote:This starter relay sticking MIGHT happen.
It happens alright. It just doesn't happen in Bumf***, Washington. Soil scientists,hydrologists and aura analysts are trying to get to the root of this local phenomenon. You may get a request for an interview appointment. Smile


__________________________________________________
1995 K75 90,000 miles
    

MartinW

MartinW
Life time member
Life time member
Twenty years + ago it happened to me just after I bought it. Points jammed closed and the  starter kept cranking no way to stop it. Eventually the battery overheated blowing the side out of the battery. I had to dowse the bike in water and get it pushed to start it. It's happened twice since but I managed to disconnect the battery. I have now fitted an isolator switch in the earth lead. Since fitting the switch it has not happened again.
Regards Martin.


__________________________________________________
1992 K75s
    

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