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Discussion Starter #1
I purchased this new tach from BKRider and the single fire adaptor from e-bay. I have my tach hooked up to an external 12V supply and the tach does initialize (0 to 8K and back)) when it is pluged in.
Each coil shoul have a - and a + and the adaptor wires should go to -
With the engine idling, when I measure from the bike ground to any of the 2 wires on each coil, I get a + reading on all 4 terminals( one red and one black). I did it again and the same + + + + readings. I know that the black should be the - and I hooked up the adapter to these terminals.
Start the engine but the tach stays at 0...
What am I doing wrong here and why the + reading from both terminals of the coil? Any help is more than welcome.
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Well from what I remember on most coils they work like this.
Power to the hot side
Wire to plug for spark to travel to
Ground wire is controlled by points or electronic ignition to tell it when to spark.
I not sure details on tach.
 

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Discussion Starter #3
Thanks, but I was asking why do I get a + reading on each of the coil terminals.
I think I will need a electrical diagram to find out.
 

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Twist tach power and light together and connect to coil red wire. (common between two coils)
Connect adapter to other two coil wires.
Connect ground to convenient black/yellow.

Your meter reads 12v on all coil leads because it cannot react fast enough to register negative going pulse with bike running.
Engine not running will give 12v on both sides of coil.
 

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Discussion Starter #7
Great ideea and thank you much. I will try tomorrow morning.
And just to aviod making any connections inside the headlamp can I just connect the tach's black wire(-) to the bike's ground(frame) and not the battery?
Also, because would be easier I will connect tach's power to one coil(+) and light wire to the other coil(+)
 

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Discussion Starter #9
I will connect the ground wire on the bottom screw of one of the coils. And do you think the reason it did not work is the fact that I had the power from the external power supply? Because this is the only thing I will do different now? Thank you again.
 

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Hmmm, with seperate tach voltages (12 volts and signal) plus seperate grounds, it may be a problem. At the very least, supply ground would have to be referenced to bike battery ground.
 

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Do the instructions say negative terminal? I don't believe there is one on a coil.
The red leads are constant 12v (+). The black (front) and blk/green (rear) are the signal leads from the ignition controller (+). The coils ground (-) through the mounting bolts.
 

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Discussion Starter #13
Steve, this is exactly what I've seen yesterday when I measured the terminals Instructions of the tach show the green connected to the negative of the coil and the tach's black(-) wire connected to the ground. My Drag Specialties adapter has the 2 black wires that I will connect reluctantly to the black of the coils. And I will get power for the tach from the red(+)of the coils.
More over, looking on the bottom of the coils I noticed that the red wires go to a green base on the coil and black wires go to a black base on the coil.
I will keep you posted later on. Thanks to all for the ideeas and help with this.
 

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Discussion Starter #14
Update: hooked up all as I mentioned. Ignition key ON, tach does initial 0 to 8K and back to 0. Light tach ON. Monitor voltage from good ground to one of the black wires from coil 12V. Start engine and monitor the voltage 13V. Tach stays at 0. And I ran out of ideeas.
 

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Discussion Starter #15
I am now contemplating removing the gas tank for the first time and look for a dedicated terminal for tach from harness if it is there.
I just don't get it. Where is the negative to coil? They are all positives?
Or get a wirring diagram and and try to understand how it works.
 

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Are you sure the tach works?
What name or brand of tach do you have?
It sounded like you have it hooked up some what right the first time.
Red to hot wire.
Ground the tach out to frame or a good ground spot.
Then your signal wire should go to coil.
 

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Discussion Starter #17
It is a new tach and it does what is supposed to: it does initial on power ON, tells me it is OK. This is a 2011 Kawa Vulcan 900 Custom special eddition.
I just think this is a new type of coil where the coil is getting the minus from the ground via the frame and it has 2 positives to each coil. But why? This is the big question and without a schematic diagram can not be answered.
I thought I new them all after riding for 40 yr.
 

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Discussion Starter #19
Sure, the adapter is single fire made by Drag specialities (sealed from ebay).
The description is Harley single fire adapter but of course should work with all tachs.
The problem is where can I connect the minus of the adapter. In any case now I know not to the coil because there is none. There is continuity between all 4 coil wires and they are all positive. Why? This it the 64K $ question.
 

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If you have wired up as I specified, the tach should work. If not, the adapter is bad or the tach.
There are NO negative or ground readings to be had on your coils.
If key on and engine NOT running, both sides of coil WILL read 12v. That is normal.

Post back with a link to your adapter.
 
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