RPM Meter Gone Crazy !
 

RPM Meter on my GS Basic gone crazy recently.

During daily ride at 4th or 5th gear and between 2500-3500 RPM, meter goes down to ZERO or up to 6 thousand RPM instantly due to throttle (and it does it at all gears and speeds).

The problem it doesn't indicate the correct RPM. It goes down and up all of sudden as bike goes at normal speed and RPM.

What can be wrong and I guess I must change the RPM meter?

Any suggestions welcome.

Sami

The ground at the ignition coil is off.

You may have an internal problem though - happenes once to me. There is a brown ground wires that goes "around" the rev-meter - it can get isolation damages and short out the meter.

Begind with checking your wire/ground at the coils - I do think that is where you will find the cause -;)

Mr lindberg - If the ground wire at the ignition coil was off .. would not that effect the ingition (ie engine spark) too?

Anyways .. the rev meter going to 0 probably indicates a wiring problem .. check the connector in the headlight shell that connected the rev meter to the main wiring loom. Could be loose, or have a bad connection. There is one wire from there to the coil ... the rest are common to other things used around the headlight area. If there was a problem with them you should see other things happening .. As you don't I think either the fault is in the connector, the wire to the coil or the meter itself.

We are describing the same thing.
It is a wire problem.

It may be at primarilly 4 different locations:
* coils
* wireloome
* instrument housing
* headlight/housing
It may be due to broken/burnt wire. Damage isolation of wire shortring it out. Loose connections.
¤ Joker - faulty rev-gauge

The most likely cause is at the coils, less the instrument housing has been opened... Of cause it is well known that the wireloome gets "worn" as it passes the steeringhead resulting in internal shortings - on the older beemers i.e. However, if I recall correctly, Samis bike is a 1992 GS - if so, his bike does not have the electrical connections inside the drivinglight but under the tank on the frame. Hence Samis problem is most likely to occure at the coils and their connections (he should have the newer 12V dual-coil and not the old double 6V coils).
So my first guess is a lose connection, i.e. the ground connection. My second guess is a damage wire (the gound wire as it enters the wireloome).

Same as my Dakar
 

I just had a similar problem on my F560GS and, thanks to the local BMW guys suggestion, i found out it was loose terminals on the battery.
I tried to troubleshoot it on the road to look for the high beam light to go out when the tacho flickered but it didnt so assumed it wasnt an electrical interruption.
So check the battery terminals first with any electrical issue. Start basic
Good luck

For my F650GS, it was the speed sensor that fried. My tach would shoot up to the red-line area, even though I knew I was in the 3500-4000 rpm range.

I had to get it down from Alaska to Washington via the ferry system (what, with garbage in, it was garbage out to the fuel injection process) where they could pull one off a new bike (none to be found in the BMW N.A. wharehouse).

So bad things do happen - not always the simple solution.