Oh, those Electrical Gremlins! I was heading home when I looked down and found that the gear indicator was showing "1". And I thought I was in 5th. Ok, so I try hitting the kill switch and turning off all electrics and back on. Nope that didn't do anything. A few miles further on I look down at the indicator and it's gone back to 5, Righto! Then it displayed "9". I didn't know I had that many gears. Then "1" again before settling on "5". Then flickering between "5" and "9". When I finally get home it's gone to "5".

So obviously it's some vibration induced electrical connection problem. Any suggestions? My first thought was the instrument pod. But before I start tearing it apart, I thought I would ask for other opinions.

best regards
J.Jefferies

The plug connector into the loom is on the right hand side, in behind or about the bellhousing to frame bolt above/in front of the alternator. 

Clean the pins in it, it may help. 

But its more liklely to be the switch itself and thats at the back of the gearbox...swing arm needs to come off to access it.

Time to remove the rear swing arm and extract the TGPI switch, then clean it. Instructions on this site.

Time to clean and repot the gear position indicator switch.  Do it as part of a full rear end service(swing arm bearings, spline lube, brakes, etc.)

The potting compound that was used breaks down and allows water and who-knows-what to get into the electrical bits of the switch.  I clean all of that old potting out and replace it with epoxy after cleaning all the springs and contacts in the switch.  I have switches that have gone over 8 years and 40,000+ miles after rebuilding. 

It is also a good time to replace the screws which hold the switch in place with Allen screws that are a lot easier to get in and out.

Point-Seven-five wrote:Time to clean and repot the gear position indicator switch.  Do it as part of a full rear end service(swing arm bearings, spline lube, brakes, etc.)

Oh, you guys are so cruel. Think I may just get the part and wait until something else needs work. I've not got a kitchen table suitable for popping the bike up on to. It's all outside on the concrete and my sad knees hate that.

You can do what I did when I was doing a lot of work on my bikes.  Get a chunk of old plush wall to wall carpet that someone put out to the curb.  About 6'x6' is a good size.

Makes crawling around the bike a lot easier and insulates your knees from the cold concrete.  Next best thing to working in your living room.

Point-Seven-five wrote:You can do what I did when I was doing a lot of work on my bikes.  Get a chunk of old plush wall to wall carpet that someone put out to the curb.  About 6'x6' is a good size.

Makes crawling around the bike a lot easier and insulates your knees from the cold concrete.  Next best thing to working in your living room.

When I lived in a house with a cold concrete basement floor I used old car mats to keep my feet, knees and butt warmer when working on bikes.

Yes, those screws that hold the GPI switch in... do NOT just try to unscrew them. You've got a very high chance of sheering them off. Clean the entire area around it first and then using a good penetrating fluid, spend a couple of days soaking them. Get an impact driver with a well fitting bit and give them a sharp tap in the tighten direction to crack any corrosion. A bit more penetrating fluid and use the impact driver to start them out.

Yes, it's a real PITA process but they're only 4mm screws and they're right in the way of all the road spray. If they sheer off it's either a specialist job to have them spark eroded or a replacement gearbox. I had the head come off one years ago and was very, very lucky that it didn't sheer flush. I could just get a pair of longnose vice grips in and unscrew it bit by bit that way.

Dai wrote:Yes, those screws that hold the GPI switch in... do NOT just try to unscrew them. You've got a very high chance of sheering them off. Clean the entire area around it first and then using a good penetrating fluid, spend a couple of days soaking them. Get an impact driver with a well fitting bit and give them a sharp tap in the tighten direction to crack any corrosion. A bit more penetrating fluid and use the impact driver to start them out.

Yes, it's a real PITA process but they're only 4mm screws and they're right in the way of all the road spray. If they sheer off it's either a specialist job to have them spark eroded or a replacement gearbox. I had the head come off one years ago and was very, very lucky that it didn't sheer flush. I could just get a pair of longnose vice grips in and unscrew it bit by bit that way.

I've taken a ton of those off and never had an issue with those shearing the heads. Never needed penetrating oil. The real pain is getting a socket well-seated on them since there's so little clearance to the side of the body of the switch.

Point-Seven-five wrote:You can do what I did when I was doing a lot of work on my bikes.  Get a chunk of old plush wall to wall carpet that someone put out to the curb.  About 6'x6' is a good size.

Makes crawling around the bike a lot easier and insulates your knees from the cold concrete.  Next best thing to working in your living room.

Got that right
I still use mats, altough have a bikelift.
Old gardenchair cussions are usefull too, have 1 in my car, just in case I need a repair on the way.

I picked up some 35mm thick pieces of laminated foam offcuts that were a bit wrinkly. One piece is squishable enough to fit in a pannier for house calls. Extremely comfortable.
Regards Martin.

No one mentioned the price. Ugh, think I'll be trying to renew the GPI/TRS/TGPI
switch before buying a new one.


Transmission Switch - BMW K Bike; 61 31 1 459 593 / BMW


Part # TRSwitch593

BMW List Price $161.61

EME Price $155.40

If you've never done it before then you don't want the clutch arm to fall too far when taking things apart as there's a big spring inside of the clutch boot that can tear it. I use zip-ties but another way to keep it from getting torn is to release the hose clamp at its base. (It's normal for there to be gear oil in it.) The clutch boot is "only" $45 at EME so it's worth the effort to avoid having it tear.

jjefferies wrote:No one mentioned the price. Ugh, think I'll be trying to renew the GPI/TRS/TGPI
switch before buying a new one.


Transmission Switch - BMW K Bike; 61 31 1 459 593 / BMW


Part # TRSwitch593

BMW List Price $161.61

EME Price $155.40

I have rebuilt five of them so far.  The worst part is getting the darn thing off the bike. 

The actual cleaning and repotting with epoxy can be done the first time in less than two hours.  I have switches I've rebuilt that have gone 40,000 miles and 7-8 years without a glitch. 

Here's my write up in another thread back in november 2021:

"I've had good luck repairing those switches, five of them so far.  The major problem is the potting compound that was put around the wires cracking and letting water carry dirt(and salt) into the switch corroding the internals and making electrical contact wonky. 

Once the switch is on the workbench you can take it apart while being very careful to not lose the tiny springs and contact parts.  Several good doses of Deoxit scrubbed with a toothbrush(use your wife's, Deoxit tastes terrible, you don't want it on yours).  Be especially fussy in cleaning out the holes the contacts and springs live in.  There is electrical contact at the bottom.

The important part is to remove ALL the old, crumbly potting compound.  It pays to take your time here to get every little bit.  Again, your wife's toothbrush will help a lot.  Soak the part in 91% rubbing alcohol and scrub it well a couple times then let it dry overnight.  Mix up some slow cure epoxy adhesive and put it around the wires where the old potting was.  Use a toothpick or wooden match stick to work it in to all the nooks and crannies and to get the air bubbles out. 

After the epoxy cures for a day or so, reassemble the switch using a shot of Deoxit to leave an anti-corrosive film on the internal parts.  Don't use any grease as it will interfere with the spring pressure that makes the internal contact in the switch.  Wrap the switch with a layer of Self-Amalgamating tape to seal it.  Reinstall with a new gasket and fillister head(Allen) screws which are infinitely easier to work with than the Phillips head screws the factory used.   This should give you a switch that will outlive the rest of the bike."

duck wrote:The real pain is getting a socket well-seated on them since there's so little clearance to the side of the body of the switch.

Yeah. I've got a ground-down 1/4" drive 4mm socket just for that.

thank you, it has been very useful