Car tach on kz 700

You're using loudhvx's diagram for factory ignition -- the blue diagram is for aftermarket ignitions...I don't see that you posted what ignition you're using. You might try to add resistence, as he suggested. Please keep up posted, I am planning this mod, just not quite there yet so I have no personal experience with tweaking the basic schematic on this.

please have a seat this is a good one !!

stock igniton
dyna grey coils
big dumb tach lol

Single Fire Adapter for VN900 and VN2000

The 1500/1600 Vulcans use a dual fire or 'wasted spark' ignition system that provides a pulse from the coil every revolution of the engine. The 900 and 2000 engines are 'single fire' meaning the spark plug only fires every other revolution for the power stroke (same as most cars).

The problem: the majority of motorcycle tachometers are designed to work with dual fire ignitions.

The solution: A dual fire adapter that takes pulses from both coils and feeds them to the tach.

You can purchase dual fire adapters almost anyplace motorcycle tachs are sold. Barons has them Mr. Fabrication has them (midway down the page) and there are others. Barons throws one in with every tach purchase so no worries if you're buying one of their very high quality units. If it bothers you to pay $20 or more for something you can make yourself for about a buck then read on.

All a tach adapter does is send the pulse signal from the negative side of both coils to the single wire of the tach thus doubling the number of pulses (and making the tach think it's working with a dual fire ignition.

What You'll Need

1- foot of 18 gauge wire (any color)
2- 1N4007 Diodes (Radio Shack)
2- 100 k ohm resistors
Shrink tubing

How To Do It

Take a look at the diagram at left (click for larger image). It's just an ultra simple circuit that allows power to pass 'from' the coils to the tach but the diode prevents it from moving backward from one coil to the other. The resistor smooths out the power delivery (eliminating spikes) but the resistance prevents one coil from being affected by the other. You 'must' use both.

Notice the way the arrow points in the diode diagram. That shows the direction the power flows. It can 'not' flow backward. If you reverse the diode the circuit won't work. So how can you tell? Not a problem. Check out the picture at right. The diode will have an off center silver band on it. The power flows toward the band as shown in the picture.

When you're finished you'll have a little assembly that looks like the picture at left. See? Simple! Solder the twisted ends and add a short length (couple of inches) of wire then put shrink tubing around everything so you isolate the two sides and protect against abrasion. Add appropriate connectors to the wire (dictated by whatever you're using to connect to the coils and to the tach wire). You'll end up with a harness that looks a whole lot like the example at right.

Connect the two 'coil' side wires to the negative side of your coil. How can you tell which is which? The negative side will always have a dissimilar color wire from the other coil. In other words, both positive wires will be the same color, the negative wires you're interested in are the two odd colors. Once connected to your coils using the same type connectors as shown for the 1500/1600's above connect the 'tach' side wire to whatever color wire from your tachometer (usually green but not always) is supposed to attach to the coil.


The Parts
Twisted Together. Note orientation of Diode So Electricity only Flows One Direction Toward Tach
Soldered

Add Shrink Tubing To Each Leg
Add Shrink Tubing Over Entire Assembly
Attach Appropriate Connectors. Done!

Make sure all your wiring is tucked up out of the way so it won't rub on any engine part or be abraded by the frame. Gentlemen (and ladies) start your engines! If, for some reason your tach still reads half the rpm it should or if it doesn't work at all recheck the orientation of the diodes.

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Wiring tip (for those who bothered to read all the way to the bottom). When pulling wire through any kind of sheathing (like shrink tubing mentioned above) it'll pull much easier if you blow a little bit of baby powder into the sheath.

You sure about that schematic? The current can back feed through the resistors, making the diodes obsolete. I mean do you actually have it wired like this, and it is not cross feeding between coils? It looks like it would cross feed.

Okay, you are putting this on the KZ700 right? That's a 4 cylinder, right?

The setup you are showing us is for a 2 cylinder that has a single spark ignition with 2 coils. That means each coil only fires on every other revolution. But, since they fire 180 degrees apart from each other, there is a coil firing on each revolution just not in the same cylinder. Left coil fires during Revolution 1, Right coil fires during Revolution 2, and so on. By tying the negative posts of the 2 coils together and using the diode/resistor network you showed us, the 1 pulse per revolution signal can be seen by the tach.
Here's the deal, by doing this on a wasted spark 4 cylinder, you are going to see 2 pulses per revolution, not one. Right and Left coils both fire during Revolution 1, Right and Left coils both fire during Revolution 2, and so on. If you are looking for 1 pulse per revolution, you already have it from just one of the coils, the diode/resistor network isn't necessary. Look at the points, or pickups, whatever, that is on the end of the crankshaft. They are located 180 degrees apart from each other. One revolution of the crank will pass by both of the pickups, you only need the pulse from one of them.

According to the AutoMeter instructions I saw, you can set your tach up for either 1 PPR or 2 PPR for a 4 cylinder, almost as if they were anticipating your application. This is why I suggested that you may have a setup issue. This might be why AutoMeter told you to simply hook it to the hot, no network (the correct term is multiplexer) needed.

so your sayin just try it hooked to the hot ? the green wire that is.? on one coil right.

the pictured setup was just tryed and no luck granted im runing 470k ohm resistor.

as for the single pulse i did not see anything on the tack site could you send me a link?

My tach is runin now 1/2 the rpm hooked to the stock ele pickup

my tach only reads 2 pulse system for 4 cyl motors my kz 700 is only puting out one pulse per rev so the tach is reading at 1/2 the real rpm.

to switch from 8 to 6 to 4 cyl i have dipswitches this is the 3 1/4 inc tach for a car 4 cyl. i didnt wana spend a ton and got this cheep now trying to figure out how to make it work..


what i need is a echo box of some sort one pulse in 2 pulse out that would give the tach what it is looking for and corect the 1/2 rpm problem

has any one tryed this or ever herd of such a device the boxes up top are lookin better and better but then ive got the same amount of $$ in this tach as the one that would have worked just right.

www.autometer.com/productPDF/1244.pdf


Please post the link to your tach's install instructions.

If you indeed need 2PPR then you will need this multiplexer you have built.
If you installed the diodes backwards your device would not work so check that out.

2- 1N4007 Diodes (Radio Shack)
2- 100 k ohm resistors (Radio Shack)

the back of the radio shack package shows the polarity of the item and how to hook up. please refere to the package if you have questions.

I found this diagram also, using the Stator for the signal. But its from a Honda Spree Scooter Forum, no i don't own one. Just a Google search on the subject. Using the Alternator is another fairly common way to get a RPM signal.

100k and 470k resistors are 100,000 ohms and 470,000 ohms respectively.

You should try 470 ohms. That's what I use on the Sunpro tach. 1N4007 may be ok diodes, but they can bleed off a little bit of spark energy. You might not notice until the RPMs are high under heavy load. To prevent that, you use diodes with a PRV (peak reverse voltage)or PIV (peak inverse voltage) around 600v to 1000v.

ready2ryde1985 wrote:

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I wouldn't expect that to work on an inline 4, electronic KZ ignition. It might work on a Dyna S ignition, though.

I have tryed evrything i think of. open to all sugestions :S

loud hvx
I have tryed the setup you are running have done dif verriations of it to see what it will do and no reading.

The last one i found used the diodes and resistors at the same point i didnt understand it didnt even care to over think it just thought hey its worth a shot lol

The issue im having is simple enough in any veryation that i hook the neg sides of the coils togther i dont get anything. if i run it to the one coil it reads 1/2 actul rpm so idk


4thekz1000
what verryation are you sugesting with the stated parts?
2- 1N4007 Diodes (Radio Shack)
2- 100 k ohm resistors (Radio Shack)

here is the link to the pdf i have the setup that shows the tach hooked to the coil neg or to the ele tach pickup..
www.egauges.com/pdf/AutoMeter/192r.pdf

ok i did not over think that one but i cant get the one you have drawn up to work on my autometer it only needs to hook to a non powerd source..

seems no mater what i do i get no reading if the two coils are hooked together im gona try the 100 k resistor and the diodes on the last page


here is the link to the pdf file for my tach im lookin at the neg to coil or green wire to the tach out put on my ignition.
www.egauges.com/pdf/AutoMeter/192r.pdf