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'80 BMW R65 Project. Bad neutral switch?

Discussion in 'Projects' started by Batcycle, Jan 6, 2012.

  1. I just bought this for a very good price


    HOWEVER, it is not running. It has some charge on the battery but I'm not sure if it's enough but the bike won't even turn over. The previous owner said that he had an instance where the bike wouldn't indicate neutral and wouldn't start or even turn over(I believe even with the clutch in) but it would shift into neutral (he could roll it back and forth). Then about a week later he came back to it and decided to try and start it just for kicks. He put it in neutral and the light came on and it started up. He rode it for a while and parked it last summer. It won't start now and he sold it to me. It won't indicate neutral for me either and it won't even turn over. SO I'm thinking it may be a bad neutral switch but I'm not sure yet and I'd like to avoid having to replace the switch if I can but we'll see. I'll let you guys know as I make progress but also suggestions are more than welcome as this is my first restoration. Thanks!
  2. It could be a NUMBER of things - bad fuse, bad connection, bad starter switch, etc. You need to get a shop manual, or at least the wiring diagram for the bike, and follow the circuit path through to figure out where the problem is. If you just start replacing things because they MIGHT be causing your problem, the odds are that you'll spend a lot of time and money needlessly.

    Seriously, troubleshooting this kind of electrical problem isn't very hard to do IF you have a schematic/wiring diagram - and if you can post a link to one for your bike, we can walk you through what to check where and how to figure out what the problem is.

  3. Good point. I've been trying to find a wiring diagram but with little success (at least not for free or in electronic form)
  4. Thank you that should help some. I'm somewhat at a loss for where to start. Hitting the internet again!
  5. jump the two wires going to the neutral indicator switch, if it starts, it's the switch, if it doesn't, it is something else.

    The fact that the bike doesn't show neutral on the light makes the neutral switch seem a likely culprit.
  6. Thanks for the link, Av. Following is based on the PDF, as it's for a US 81 - the color diagram is possibly for a european model (and the pdf is clearer, too).

    20 is the start switch, 24 is the starter relay, 25 is the neutral switch, 39 is the starter (which apparently has a starter solenoid mounted on or in the starter).

    The start relay, 24, has a coil which must be energized for its contacts to close and pass 12v to the starter. For the coil to be energized, it must have 12v on one side and ground on the other. The 12v comes from the start pushbutton, 20, on the wire marked 0.75blge. The ground comes from either the clutch switch, on the wire marked 0.75brge, or from the neutral switch, 25, through a diode inside the relay. If the start relay has 12v from the start pushbutton and ground from either the clutch switch or the neutral switch, it energizes and closes contacts that pass 12v (which gets to the relay on wire marked 1.5rt) to the starter, 39, on wire marked 1.5sw. The reason there are separate connections for the clutch switch and neutral switch is that the diode inside the relay isolates one from the other so that your neutral light doesn't blink at you every time you pull in the clutch.

    Troubleshooting? First, find relay 24 and identify the wires coming to it. Use a meter set to DC volts, or a test light. Ground the negative (black) meter lead, or the test light's lead, to the frame. Use the positive (red) meter lead, or the test light's probe, and make connection to the 0.75blge lead. With the ignition switch on, push the starter button - if your meter reads 12v, or the light lights, that part is ok. Now make connection to the 0.75brge lead, and with the clutch released and the transmission in gear, push the start button - if the meter reads 12v or the light lights, the relay coil is ok. Try again with the clutch pulled in - if the meter reads 12v or the light lights the clutch switch/ground has problems. Now put the transmission in neutral, clutch released, make connection to the 0.75brsw lead, push the start button - if the meter reads 12v or the light lights the neutral switch/ground has problems.

    Once you've identified the problem, follow the wiring from the relay to the problem (clutch switch or neutral switch) and repeat the test with your probe on the -switch- end of the wire. If results are the same, the switch is the problem - if the meter doesn't indicate 12v/test light light, the problem is in the wiring/connectors between the relay and the switch.

    Clear as mud, right? :mrgreen:

    Hope this helps
  7. You are awesome this is my day today and tomorrow
  8. It will never work. You should just sell it to me cheap. Nice find , if you don't mind how did you have to pay for it?
  9. again, the quicker test as it certainly seems like the neutral switch, is to jump the neutral switch wires and see if it starts. This will take 10 seconds and if it is the switch, will save you hours of troubleshooting. Keep it simple first.
  10. Just scrap that engine and toss a Rotax twin in there!

    (But seriously though, nice find! I'm actually looking for one just like it!)
  11. :nana
    I don't mind at all $500.
  12. From the original post, it appears that the clutch switch isn't working, either - so I thought I'd give him the information to test (almost) everything concerned. And once he locates the relay, the rest of the tests are only going to take a few minutes. If you stall at a light or on a hill, MUCH nicer if you just have to pull in the clutch and hit the button to be going again, rather than having to get into neutral, restart, select first, then try to get going again. And for what he paid for it, I'd imagine he's going to need to get pretty familiar with it anyway......
  13. I officially hate you......

    Congrats on a nice find!
  14. Wow! That is a steal, if you want to sell it, Me me me. :mrgreen:
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