Scott
thanks for the quick reply.

13.16 volts on the battery. If I "jump" the BR/SW wire to the BR wire at the switch the green neutral light comes on. I checked the washer/crush on the original switch and it's thicker than the replacement washer, almost twice a thick. I'll have to drain the tranny and pull the switch. I'll have to bench test the new switch, which is the Siebenrock brass version. I'm wondering if I should use the original washer with the new switch?

I'll work on that tomorrow and let you know how it came out...
redhorse

13.16 volts on the battery.

If that's with the engine running at road speeds, then that's too low. Looking for about 14.2V. If that's with the engine stopped and everything turned OFF, then that's too high. Looking for 12.8-12.1V, depending upon the age of the battery. Higher is 'gooder'.

If I "jump" the BR/SW wire to the BR wire at the switch the green neutral light comes on.

That's a good thing becasue the bulb is the FIRST thing to check, even though they can be hard to access. I've had VERY good luck inserting the green LED from SuperbrightLEDs.Com which allows easy viewing even in bright sunlight.

I checked the washer/crush on the original switch and it's thicker than the replacement washer, almost twice a thick.

That only means that particualr switch has been judged to need a thicker wash. And that's all. Don't draw any erroneous conclusions just based on that one fact.

I'll have to drain the tranny and pull the switch. I'll have to bench test the new switch, which is the Siebenrock brass version. I'm wondering if I should use the original washer with the new switch?

You should start by bench testing the switch as per Scot. Then you should reinstall the switch and test it in the tranny with an Ohm meter connected directly to the 2 contacts. (Harness disconnected for all tests.) You should see a definite Make/Break correlation on the meter in and out of gear.

Then, if you don't see that Make/Break action of the switch THEN you can try different thickness washers. Remember it's just as likely you'll need BOTH washers as only the thin one. Keep your mind open to creative solutions.

Re-seal the switch by applying LocTite gasket maker #518. Click Here

The diagram also shows the wires go to none side of a diode. Does the diode reduce the voltage? Wouldn't think so.

No, the diode acts as logic in the circuit. You are forgetting that the Neutral Switch not only allows the illumination of the Green dash lamp, but also tells the Starter Motor that it is safe to allow the electric starter to operate.

If readings are allowable at the switch, then it is FAR more likely that your Starter Relay is having trouble, ESPECIALLY if your bike has the under-fuel-tank Brake master cylinder. The under-tank brake m/c is famous for puking brake fluid all over that relay and all its connections. In fact, every electrical connection in that area should be spray washed with HOT soapy water, and then EACH connector re-seated with a dab of NO-OX-ID to restore the good electrical connections. Click Here

A single Brown/White wire enters the headlamp shell, but only attaches at a single point to the multi-color connection board at the Brown/White connection area on the board, which is found at the 3:30 position.

Gentlemen,
Thank you for your responses.
I believe the problem was solved with your knowledgeable input.
- Battery voltage 13.1 v with bike off, on charger. New battery.
-The bulbs were replaced with LED bulbs. These bulb, I found, are polarity sensitive. solved that part of the puzzle.
-The crush/spacer washer that came with the new neutral switch (NS) is only 1.3mm thick. The original washer is approx. 3mm thick. Looked up NS on Boxer2Valve site for this year bike http://www.boxer2valve.com/Merchant5/merchant.mvc?Store_Code=bmw2valve&Screen=PROD&Product_Code=6131097 and they have attached a short video explaining the NS continuity test. Basically; button released (neutral) circuit is closed light comes on. button depressed (in gear) circuit open light goes out.
- Bench tested the switch, at rest-continuity, depress button-open circuit.
- Tested NS with wires attached, out of tranny, green light comes on, depress button, light goes out.
- Installed NS back in bike with thicker washer, everything works as it should.
- As for low voltage reading at wire for NS, ??? Green light is a bright as other lights. All the LED lights are brighter than OEM incandescent bulbs, especially the blue high beam indicator.
- Did find the BR/SW (brown/black) wire in the light bucket behind the BR/GE (brown/yellow) wires in the terminal board.
- 81 RTs have MC on handlebar, everything under the tank is dry. Did clean up the fuses, some PM.
Wobbly- thank you for that picture of the terminal board.

Just wanted to say thanks again for all your help.
Airheads rule
redhorse
81 R100RT
-

....
- Battery voltage 13.1 v with bike off, on charger. New battery.
-The bulbs were replaced with LED bulbs. These bulb, I found, are polarity sensitive. solved that part of the puzzle.

Not finished yet !!

• Are you measuring the battery voltage with the shop battery charger still connected ?? WTF ?? You are simply reading the voltage of the charger, NOT the battery. Disconnect that thing right NOW !

• What type of "new battery" ?? That would need to be an extremely nice battery with a voltage of 13.1V, or the high voltage could indicate excessive charge voltage which will severely shorten the life of your battery. Start the engine and run the RPM up to 3000 and hold it. Place a DC voltmeter across the battery terminals and see what it says. Should be between 14.1 and 14.3 depending upon battery style..... AGM, Flooded Cell, Gell Cell, etc.

• Did you also replace the dash board Alternator warning lamp with an LED ??? You cannot do that. The resistance of the incandescent bulb is a INTEGRAL part of the charging system. The regulator depends upon the internal resistance of an incandescent.... which the LED cannot provide. This could be having a negative effect on the discussion above. You need to booklet from Mottorad Elektrik explaining the charging system.

Hope this helps.

OK OK OK
Took maintainer charger off, voltage is 12.7 . Can not start the bike right now due to waiting on parts. Will check asap.
Battery is <one year old, AGM style, brand name: Auto Craft, model: ETX16L, 325 CCA. Fits very well in the battery area, just slightly smaller than original.

I installed the EME EnDuraLast alternator kit system a few years age. System works great. I believe that the GEN light is not part of the charging system circuit, as in the original Bosch system, where if the bulb burns out the system stops charging. Putting an LED bulb in will only work with the brushless permanent magnet 450 watt system.
EME says "you can LED all you want". I'd check with EME about any other charging system.

Thanks for the input. It's good to have your work checked by a second set of eyes.
redhorse