tach not working/hookedup

[Patrick_Krivacka]

Barry, problem is my coil is very non-original. i have a photo of the coil that the PO rigged up in the thread titied 'weak battery? '.
Monte, good suggestion on checking with the manual.

[Barry]

my coil is very non-original.

It doesn't matter what the coil is it will still have two connections :-

One will connect to the the ignition switch via the engine stop. Original wire color green/blue.

The other will connect to the points or ignition module. Original wire color Black.  The tacho wire doubles up on this connection.

[Patrick_Krivacka]

thanks for that barry. Assuming (yes, i know all too well what happens when you ass u me) that that is the tach wire, what would I need to contrive to get the connector in the photo to connect to the coil? Would I have to hook some kind of male connector to the coil? other?

[montmil]

...what would I need to contrive to get the connector in the photo to connect to the coil? Would I have to hook some kind of male connector to the coil? other?

Check out a solid hardware store like Ace or a Radio Shack or similar and prowl through the electrical connector bits. From the photo, it's hard to tell what you've got with your "fence post" coil rig, but you should be able to fab a workman-like attach point.

Monte

[Patrick_Krivacka]

'workmen like' is something I'm comfortable with. I'll see what i can work up after figure out that it is, in fact, the wire for the tach. thanks all.

[Rob Valdez 79 R65]

i-man,

There are brass or copper spade connectors that are 'U' shaped, with the arms of the U spread out a little.

On the flat, or bottom of the U, is a hole for the nut & threaded stud connector on most coils.
Finding these on a shelf might be a little hard.  You might try an auto parts store, too.
If worse comes to worse, I have a couple of old ones on my old coils I replaced a few years ago.

Please check these two wiring diagrams (depending on the year of the wiring harness):

1978-1980

1981-1984

[Patrick_Krivacka]

thanks for the links rob. one (of many) things I don't understand about wiring diagrams, is how do I determine that this one wire is the one for my tach? I mean, it just pops out of the harness, so how do I trace it back to the tach? also, a few people have commented on my instrument cluster being originally for a bike other then the r65. how does this fact fit into the equation?

[Rob Valdez 79 R65]

thanks for the links rob. one (of many) things I don't understand about wiring diagrams, is how do I determine that this one wire is the one for my tach? I mean, it just pops out of the harness, so how do I trace it back to the tach? also, a few people have commented on my instrument cluster being originally for a bike other then the r65. how does this fact fit into the equation?

What color is the insulation?

Brown is ground.

I think there is a green (or green/blue, as Barry said) or a combination of these two that connects to the coil.

I'm not sure what the black wires are for.  (I am at work, and I can't see the wiring diagrams.)
But they are not ground.

[Patrick_Krivacka]

thanks for the fast response! i'll have to check, but it's black with a ? stripe. i'll look tomorrow. any thoughts on how the non r65 cluster fits into this puzzle?

[Rob Valdez 79 R65]

any thoughts on how the non r65 cluster fits into this puzzle?  

Speedometer - no problem.

Tachometer - look at the leading edge of the instruments, down below, and see if it has a place to put a tach cable with threads for a retaining ring (just like the speedometer).  If that is what you have, you will never get it to work with your R65 engine.  The older engines had a cable take-off at the bottom-left side of the timing cover.  It probably drove off the camshaft.

The various lights were hooked up to the R65's wiring harness as best as they could manage, I expect.  It wouldn't be real hard, but it would make a mess of something.

If you want a working tachometer, you will need to replace what you have.
BMW has one that is identical to yours, but electronic.  I suppose you could just replace the tach side.  It's been a long time since I've seen the inside of one of those clusters.

Or, if you don't mind going hi-tech, you could get one of these digital clusters like a couple of the guys here have done.  That will give you a tachometer, I believe.  (and a bunch of other goodies).

[Ed Miller]

The diagram posted by Rob above only shows a brown wire going to the tach.  I'm not sure how that's even possible.  I just had the same wiring diagram printed up here at work full size color (19" x 28") and laminated.  These people sure are friendly.  

[Patrick_Krivacka]

thanks ed. I hope to be able to look into it this weekend and I'll report back. Is there a problem with riding without the tach? I sure hope not!

[nhmaf]

I-man, just don't over-rev the engine without the tach on there and you should be fine..

Ed, I checked the diagrams from Rob's links and they appear to be basically the same diagrams as that are found in the Haynes manual, though it appears perhaps someone tried to correct/augment the Haynes manual's diagrams because the Haynes manual doesn't even show the tachometer at all (at least my copy doesn't)

I checked my Clymer manual, which has the wiring diagram drawn different (and is harder to read and not colorized) but at least it does show the tachometer in the circuit.   The tachometer wiring shows that it should have (3) wire connections:  
a Brown wire (to ground)
a Green/Blue wire (to +12V power with keyswitch on)
a Black wire going to the primary (low voltage) side of one of the coils - it actually shows it connecting to the same terminal on the coil that the ICU wire does (81-84) or the Black wire from the condensor (78-80)

Hope this helps,
Mike