R1100S rev counter working intermittantly

[Two Stroke Cat]

Hi, need some advise on this issue.
Bought this 2003 twin spark model with broken engine last year.
My friend changed the engine now and it's running nice.
Don't know, if the problem was there with the old engine ( there is only 6 month between the old and new 2004 engine ).
However, the rev counter works intermittantly or only for short period of times.
Sometimes, it happens when engine is idling, but not on higher revs and vice versa.
Before I strip down the lot to get access does anybody know what could be wrong?
Thanks in advance.

[Paul]

My first line of investigation would be to take off the left hand front fairing and see if there is any damage to the cables running along the front sub frame from the left hand fuse box. They are quite prone to rub against the sub frame and wear through, with occasional contact with the metal of the frame temporarily making a circuit again and leading to the intermittent operation of whatever device the wire was controlling.

Cheers,

Paul

[tanneman]

The Haynes manual has a good electrical scheme to aid in fault finding. Probably a poor connection (check for corrosion on the pins) or a wire chafed through.

[Two Stroke Cat]

Thanks both for the advise on these models - it's my first BMW bike !
Will investigate next weekend.
Also noticed, that the digital clock display doesn't work either.
Will get there in the end .......

[Paul]

if the clock is not working too, it sounds more and more likely that it's wires rubbing on the front sub frame and wearing through. Easy enough to fix by splicing in a new bit of wire and going overboard on insulation tape before you put it all back together.

The tell tale sign is blue/green copper oxidation stains on the black wiring where the insulation in the wire has worn through.

Good luck

Paul

[Turbonutters]

I had a similar problem on my S.
In my case the connector's pins were badly damaged.

[Two Stroke Cat]

Hi,
yes, I've found the connector pins corroded and one - top left - missing !
It's on the big blue connection in the relay box. It's the red/white wire.
I will bypass the one and see what happens.
I think the other two next to the broken one are corroded badly and I cannot clean them.
Will bypass wire them next after red/white one.
Checked the wiring loom and and it's generally solid and undamaged.
However,
somebody has repaired some wiring going into speedo/rev counter housing, so I will check them next week.
I've taken off most connection (on back of housing) and cleaned them as they were rusty - but this made no difference
Next problem is to sort out the ABS problem.
Thank you all for your helpful comments

[Turbonutters]

If I remember correctly the red and white is for the clock. Same one was missing on my bike.
I fixed it by taking 'n needle out of my wife's clothing repair box.
Press the needle into the female connector and cot it the correct length.
Now the clock is working properly.
I hate wires that bypass plugs. Unsightly and make future disassembly difficult.
I did however redo my bikes wiring harness now all the wires fit under the tank

[Two Stroke Cat]

Hi,
unfortunately this weekend I was bad and couldn't do a lot.
Investigated further around wiring loom and found some repaired sections in areas near the sub frame.
So, there must have been a problem before.
I've looked closer into the blue multi pin plug and found another 2 pins corroded and shorter than the others.
Contemplating buying a second hand wiring loom to replace that section now.
I will try the "needle" option next before I buy a part wiring loom.
I hate bypassing plugs with wires, too.

[Two Stroke Cat]

So,
finally got around investigating.
All wiring OK and checked with multimeter.
Found the top left pin broken in blue connector ( not three as previously mentioned ).
Replaced with needle pin from sewing kit and clock working fine THANK YOU Turbonutters

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Went for 100 mile ride and Rev counter worked once for 3 seconds.
Cannot see anything wrong with wiring, so must be faulty Rev counter or where does the signal come from?

[nab 301]

So,
Cannot see anything wrong with wiring, so must be faulty Rev counter or where does the signal come from?

The only R1100S wiring diagram I have is in the Haynes manual.... but it doesn't appear to be complete., on the diagram marked '01 onwards The tacho connection as they label it is to the black wire that runs from the ignition coil , (junction marked Z1 ), to the motronic unit , junction marked 35 and Z1. Tacho connection marked 16. Other R11xx model wiring diagrams show 2 other wires running from the Tacho to a fuse box.