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Discussion Starter #1 (Edited)
Adding aftermarket tach/speedo , where to pick up RPM signal

So I bought one of those cheapo tachs off Amazon for about 35 bucks. Yeah I know its not much for a tach, but this is more of an experiment as anything else and as such, I didn't want to put much into it.

I've got the thing to power up, and the speedometer function seems to work (like a bike computer, it relies on a magnet passing a sensor). It came with no instructions but I was able to print some off and even with that, I've got some of the indicator lights to work as well.

For the tach, it was suggested that a wire wrapped around one of the plug wires would provide enough of a signal that the gauge would pick it up and show RPM. But that hasnt worked. Looking on the right side of the bike (facing forward), I can see where the plug wire plugs into something that maybe a coil or something like that. It also has a red and green wire on the other side. Would one of those work as a signal to the tach?

This is the device in question:

 

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Electronic tachs usually take the signal from the negative side of the coil. Should be the black lead on the coil. If they say the lead should be wrapped around the plug wire that means it's inductive pickup. I'd look for more info before hooking that wire to the coil. Don't want to risk damaging the igniter.
 

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I just looked at the wiring diagram. Black/white stripe and red wires are for coil #1. Red/green stripe and red wires are for coil #2. Hope that helps. Be careful that the tach doesn't cause a short! Find more connection info rather than experiment. It could be costly.
 

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I found it on Amazon. LINK



The hookup info they provide leaves a LOT to be desired but if you get it figured out please post how you made it happen as I'd like to have a tach on mine. Did it come with any mounting hardware? It doesn't show any in the pictures.
 

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Discussion Starter #6
Thanks for the replies so far. So looking at the coil, pulled off the green wire and stuck a small alligator clip on it and put the connector back on. Fired up the bike and this time the tach was working ...:grin2:

Since these things are so cheap and reliability is so dicey, I wanted to make sure the major functions were working before I went ahead and started to modify the gauge. They ship it with connectors that probably fit some Chinese made bike, but nothing you would probably find elsewhere. What they don't ship with it are any instructions or directions. The color codes that are referenced in the instructions posted in the Q&A may or may not match. On this one they don't or at least not all match, but it seems like the position in the connector is reasonably reliable.

Besides getting a tach, I wanted something that would let me see if the turns were on or if the bike was in neutral. It makes no sense to me to put it all down on the tank so you have to take your eyes off the road to check your speed. And even the short time I've had it, I've lost track of how many times the turns were on well after I turned. :(

So next up is to fabricate some sort of mount for the gauge, I've already got a clamp for the handlebar. After that, I'll start hard wiring it in.

And I did look at better gauges, Koso, Vapor and I think Acewell all looked much nicer, had instructions and connectors for all the sensors but were all north of 150 and some well past 200. But I wanted something cheap enough in case I decide to sell the bike down the road. For such a cheap price, the quality isnt bad at all, it feels heavy enough and the fit and finish are actually pretty good. You just have to be fairly handy at wiring and figuring things out without much to go on to make these things work.

I'll post more pix as I go.
 

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Discussion Starter #8
Good stuff. Thanks for the update. Does it come with any mounting brackets?
Nope, nothing. It's like you bought a replacement part and the expectation is that you just plug it in. It did come with the speed sensor cable and some small magnets that go on the wheel. It looks like I might be able to mount the sensor on the front disc brake bracket and most likely can epoxy the small magnet to the rotor, in-between the mounting bolt holes. Some of the higher end gauges actually come with bolts that have a magnetic head that you swap one of the originals for, but this isnt so sophisticated.

Last night I ordered a kit off amazon to either adapt or make up new connectors. They look very similar to what is on this thing right now and I'm sure I'll find uses for them down the road with two other bikes and other projects.

 

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I agree with your point about the speedo in the wrong place, and I'd never buy a bike like that.
Go get a 1995 or older 500 they have it where it belongs, at the handlebars!
 

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Discussion Starter #10
I made some progress working with the tach. I scrounged around the garage, but didn't have any aluminum stock that I thought was big enough or thick enough to make a sturdy mount. But I did have some scrap Starboard plastic, which is a common material used for custom stuff on boats. So I went ahead and cut a small square and went about drilling, cutting and sanding the edges. After one screwup, I had a mount that worked well enough. I'll probably try and spray it black to match the gauge and the mounts.

I then went to work on the connectors. I had ordered a kit from Amazon which came today. Turns out, its the exact same connector type that is on the tach. I thought it would be from the pix, but you never know for sure till you have it in your hands. My test wires using some 18g nails had stretched out the female connectors, so I replaced them all first. Then I went on to start up the male side, one at a time.

I had gotten all the lights to work except the N or Neutral light. Just by chance, I tried a ground wire in the 6 wire connector, the one used for the shift indicator and there it was lit up. Turns out grounding out each wire in that connector set the digital display to a different number. Of course this poses a bit of an issue, since I had originally thought I would just tag a wire to each light in the speedo and use that to light them up. Since the N from the speedo is 12v+ and the tach uses a 12v- or ground, that won't work. What I think I can do us use a small relay that runs off 12v and use it to connect that light to ground and make it work.

What I haven't been able to do yet is get into the setup menu. According to the instructions, you hold a button on the back and power the gauge. I get into some type of setup menu, but not the "ccc" setting you are supposed to see in order to set parameters like the front wheel diameter so the speedo is accurate.

A few more pix of the progress:
 

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Discussion Starter #12
I found where the neutral switch sits, it's under the cover by the engine chain sprocket. And as I thought, it goes to ground when in N, so I can tag a wire on that for the light on the tach.

While I had the cover off, I went ahead and gave the chain a good cleaning and then sprayed a waxy chain lube on that.

Finally I happened to come across a Youtube video by an Aussie that talked about how to set the values in setup. Haven't had a chance to try that out yet, but its the most I've had to go on since no where else have I found anything that says what each setting is supposed to mean.
 

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Discussion Starter #13
Update on the project.


I gave up on the cheapo tach, I could have gotten everything working except that the tach would always show the RPM as double its actual value. Here's why. In the setup function one of the entries is for 1, 2 or 4 cyl IIRC. IF you change it from it's default of 1, you can NEVER change it back. Early on playing with the tach (absolutely no instructions shipped with it or even available from the vendor) I set it to 2 since it was a 2 cyl motor. Go figure. But, since it was taking a signal off one cylinder only and not both, then it would double the speed sensed. So I ended up ordering another tach, but this one was a bit more expensive and had everything with it, instructions, mount, hardware to mount the speed sensor. Nice quality gauge too, and this one was chrome with a white face which looks nice on the bike.



It's made by Koso, has the idiot lights on the front and can support multiple types of engines and wheel sizes. It took me a good day to install it, figuring out the wiring as I went. Like with the other gauge, I had a hard time getting into the setup function, but eventually I figured it out, you press both buttons at the same time for 3 seconds and you're in. You can set the shift light RPM, Clock, number of cylinders, number of magnets on the wheel, wheel diameter and you can input the bikes current odometer reading and it wall carry on from there.

For a while I couldn't get it to go from KPH to MPH, but eventually I did something while fiddling with the settings and it was now in MPH. And surprisingly it was pretty accurate, at least compared to the mechanical speedo. Right now I have it set for one magnet, but they give you a bunch, so I'll probably use either 4 or 8 and position them on the disc inline with the bolts. For testing today, I just left the magnet stuck on the disc, but I'll probably use some superglue or epoxy to make sure they don't move. The more magnets it uses, the quicker it will update the speed in the display.

Here are some pics of what it looks like:
 

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Discussion Starter #15
That is sweet! It almost looks like you make a filler ring and mount it in place of the factory speedo. It's this one, right? LINK
Thats it, but I paid 158 only a week ago. So far I like it, nice to know the rpm's and I can now see if the turns are on.

$180.00 puts it WAY out of my budget though.
 
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