The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Graeme on November 13, 2010, 04:29:24 PM
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Hi All - When I pull in the clutch, the Neutral Light comes on.
Is that normal. It renders the light pretty useless as you know that you are in netral when you've got the clutch in but you could be in any gear? :-?
Thanks
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There are 2 switches in the circuit - one at the clutch lever on the handlebar, and one on the bottom of the transmission. Most likely one of these switches has failed. But I could be wrong, as it could also be a "false ground" is causing it, but that would probably point to the upper switch. You might take that switch off the perch and see what is going on.
I understand basic electricity, but that neutral circuit confuses me (doesn't take much).
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There's a diode inside the starter relay, it's gone bad and needs to be replaced .
It's a simple job, if you know how to use a soldering iron .
You need a common diode, 1N4001 will work .
Here in North America, we have a chain type consumer electronics store called Radio Shack, they stock electronic components like this, don't know what you have in your corner of planet earth .
You could also replace the relay, if you didn't want to replace the diode itself .
If you are wondering why a diode in the starter relay would cause this, there are two switches that prevent the starter from engaging if you are in gear, the switch at the transmission is one, the other switch at the clutch lever over rides the neutral switch at the transmission if the transmission is in gear, when the clutch lever is pulled in then power is allowed to go to the starter relay and rotate the starter .
When the diode fails in the mode of allowing electrical power to flow in both direction the light bulb in the tachometer gets power when the clutch lever is pulled in .
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I always forget about that diode! Thanks, Bob.
That is another place I haven't been yet. (the inside of the relay, not Radio Shack!)
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Rob, on the '79-80 year bikes, the diode is located in the wiring harness, not in the relay .
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Rob, on the '79-80 year bikes, the diode is located in the wiring harness, not in the relay .
Thanks again, Bob!
After you said that, I began looking at the wiring diagram (http://www.pbase.com/tomfarr/image/121670650/original), and saw a second diode in the wiring, as well.
I forgot about the redline LED on the tach that the early models had. Mine hasn't worked in a long time.
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OK, Thanks. Mine's an '84 & a copy of the Wiring Digram came with the bike + I've the Hains Manual.
If it's easier, I'll replace the relay.
Thanks
Graeme
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If you get a relay from other than a BMW motorcycle parts supplier, the relay may not have the diode installed, as it's only used in the motorcycle application .
A lot of these relays were in common use in European cars from the same era .
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Can anyone tell me where in the wiring harness the diode is on a '79 model - i've looked & can't seem to locate it.
thanks, Bill
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Bill, the diode is inside a round cylindrical black plastic housing about 2 inches or so in length and about 3/8 ths of an inch in diameter with push on type terminal ends sticking out of it .
It will be wrapped up in black cloth tape .
So look for a good sized 'bump ' somewhere in the wiring harness .
You can disassemble the housing , de-solder the diode from the terminal ends and then solder in a new one .
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1N4001 diodes are amongst the most common and cheapest electrical components in the world. Should be available anywhere and cost literally pence. You can buy a pack of 100 diodes for £1.00
Motobins sell them for £2.50 each which is a few thousand percent profit margin.
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One still needs to heat-sink a diode when soldering it, doesn't one?
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Ideally yes but if the leads are left fairly long I probably wouldn't bother.
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1N4001 are fairly rugged little diodes, they can withstand fair amount of heat.
operating range is -55 TO + 175'C
Just remember when you are soldering, you need clean wire, clean diode leads, and the finished solder joint should look shiny and smooth. If not you could have a dry joint which may cause you more grief.
The secret to a good solder joint, you place a small amount of solder on the soldering iron, this is your heat-bridge, then use this to heat the wire/diode lead. You then apply the solder to the wire/lead NOT to the iron. The wire needs to be hot enough to melt the solder, that way the solder takes to the job. Normally the iron sits under the wire, and the solder is applied from above. take the solder away when it runs and wait one second more before taking the iron away.
A second set of hands or clamps will stop the joint moving when you move the iron away.
John
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On the R65 (LS) there's a unit called a "diode board" & it's mounted on the Timing Chain Cover. I'm just wondering if you replace the whole thing?
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Graeme
Do you mean the diode board inside the front cover ?
That is the main diode board which converts the AC output from the 3 phase alternator to DC for battery charging.
It has a number of large and small diodes and there is no reason why they can't be individually replaced if you know that one of them is faulty. The large ones in particular would need to be carefully soldered as they are passing a substantial current.
However your original neutral light problem is nothing to do with this diode board.
Bob has given you the possible locations of the single diode which can cause your problem depending on the year of your bike. If it's an LS
I think the diode is in your starter relay.
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Thanks Barry, I'd gotten myself confused. :)