BMW K bikes (Bricks)

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1Back to top Go down   K75RT will not start Empty K75RT will not start Wed May 27, 2015 1:53 pm

George R

active member
active member
Have a serious problem with my K75 in that it will not start.  The history is : put the bike away in the garage after a run and no problems.  Was away for 2 weeks and on return to use bike found the display was blank - ie no clock.  Switched on ignition, still no display and no start. Disconnected battery (10 months old) and fitted charged spare. On touching the live to battery a small puff of smoke from near starter relay. On connection Ignition  light , oil and ABS lamps lit.  Tried again but the bike sounded as if the starter was not getting enough power to turn and battery definitely losing power, but on using meter battery still full charge.  Replaced the starter relay - no change. Changed the starter - no change. - both relay and starter refitted to other bike - work perfectly. Took green button apart and cleaned it. Put all back together again and turned ignition key. Pressed green button - starter turning very slow and does not stop when kill button pressed or ignition turned off. Only stops when power cable taken off battery. Have checked wiring as far as I can for damage but nothing visible.  I have not had to delve into the wiring much and this is beyond my experience.    My feeling is there is a dead short somewhere but I do not know were to look. Any help would be much appreciated.
Thanks in advance.


2Back to top Go down   K75RT will not start Empty Re: K75RT will not start Wed May 27, 2015 6:15 pm


active member
active member
I am very (very!) new to K bikes, but if the starter is staying on after you stop hitting the starter button, from an electrical point of view it is probably one of two problems. First is the starter relay contacts have welded shut. Second is that the energising power to the relay is still present = stuck switch. Like I said, I am new to K bikes, but logically, these sound like the first things to check.




3Back to top Go down   K75RT will not start Empty Re: K75RT will not start Wed May 27, 2015 10:22 pm


Life time member
Life time member
Yes. Definitely the relay. Low battery will cause contacts to weld. They're easy to open up and have a look at the contacts. You may be able to clean it up but only as a temporary measure to get you going. Replace with this starter relay from EME. Don't buy second hand off ebay because its likely to have worn contacts and you'll be in the same position soon enough down the track.

BUT you have to address why that happened in the first place. I'd say the contacts were in bad shape because you have had a dud battery for a little while. Starter relays don't like batteries with little to no charge. Must be minimum 12.5V. You may have had a depleted battery because it hasn't been charging from the alternator properly. You should be getting around 14V at >2000rpm across the battery terminals. If charging is a problem then you probably need to check the alternator brushes. The regulator and brushes come in the one unit and you can get that also from EME. Even just taking it out and giving it a good clean and deoxise the connection will help

Another thing that could be causing the problem is the starter motor brushes. Easy enough to check. Also make sure the casing is contacting with the GB casing (two bolts at the rear) as the starter needs to earth properly thru that bed.

The earth connection for the battery on the GB is another often neglected connection and should be kept very clean. Problems with these connections and the starter brushes will result in higher current draw when cranking resulting in fritzed starter relay.

All connections and terminals should be cleaned and deoxidised


1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 K75RT will not start Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90

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