eBay Motorcycle Tachometer wiring

Phabbits

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Aug 7, 2017
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Hello again!

I finally got my GT90 conversion kit working, timing was off, and wanted to add a tachometer for fun. I got everything wired up expect the tachometer speed wire. The tachometer that I got was from eBay, https://www.ebay.com/itm/Universal-LCD-Digital-Motorcycle-Speedometer-Tachometer-Odometer-for-Motorcycle/263087620579?hash=item3d413e81e3:g:Ai0AAOSwpHFZaC3f, which I am now realizing is probably just for four strokes. Although, I got it working for a bit, using the blue wire from the magneto for the speed sensor, but I think I burned it out after messing with the connections. I got another tach because I really like the way it looks, but I am hoping that someone can guide me on whether or not that is a good place to attach the speed sensor wire.

I did find this reply on a YouTube video for it that does give me hope,
tach4.JPG


Thanks for the help!
Phabbits
 

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Phabbits

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For anyone interested, I have progressed slightly. I have discovered that the problem I am having is that the tachometer was designed to work off a four-stroke engine, and receive a 12V signal. When measuring the output from my magneto, I found it to be around 40V AC. While researching to remedy this, I found the following YouTube video,
Which described how to convert the signal, and use a tachometer on a two-stroke outboard engine. I recreated the circuit from the video, see my first attachment, and I connected it to the bike with no luck. Upon investigation I found the new output voltage to be around 7V AC instead of the 12V it needed to be.

Attempting a different strategy I decided to connect it to my 12V generator I had added on the bike, the one you can buy off of eBay to be added next to the magneto, and it worked fine after reaching 6000rpms. After looking into it, I found that the generator did not reach 12V until nearing 6000rpms, and usually ran more near 6V.

So, I have decided that I have to major paths I could take, first would be to modify the circuit I found to increase the voltage from 7 to 12, or secound would be to create a new AC boost circuit for my generator add on.

Love to hear your thoughts,
Phabbits
 

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outatime88

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Sep 9, 2017
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I wonder if an Arduino can be used to construct a tach. I'd imagine it would make things a bit neater instead that mess of wires.
 

Phabbits

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I wonder if an Arduino can be used to construct a tach. I'd imagine it would make things a bit neater instead that mess of wires.
Ahh yes, I did end up moving my battery to the front of the bike to help clean up the wires. Also, are you suggesting replacing the tachometer that I got with an Arduino?
 

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motorizedbikeguy

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Apr 11, 2017
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A digital Arduino-based tach and speedo using hall sensors is the route I've chosen for one of my builds. It's low-power, customizable and you can get away with having a 5v electrical system with a 6V battery. There are very bright 5v LED headlights and tail lights out there. You can even get them with a USB connector, so the entire system can be USB-based.

 

Phabbits

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Aug 7, 2017
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A digital Arduino-based tach and speedo using hall sensors is the route I've chosen for one of my builds. It's low-power, customizable and you can get away with having a 5v electrical system with a 6V battery. There are very bright 5v LED headlights and tail lights out there. You can even get them with a USB connector, so the entire system can be USB-based.

I am very curious on how this Arduino-based tach system looks like, and I would love some more information on how you used hall sensors to do it.

As for the lights, it is very impressive that you have been able to create a 5v system which is entirely USB-based. I was going for a system that was a lot closer to an automobile, because I currently have a summer job at an auto parts store, so I am able to get parts like 12V bulbs and lights cheap from there, and I want it to be very easy to get parts in the future.

Motorizedbikeguy, maybe I can adapt your hall-sensor system to work with my meter, big thing being that it has an analog style needle display for rpm, which is really the reason I chose it versus the digital "Tinytach"s available on eBay.
 

JerboaJohn

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Jul 29, 2018
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what about those old 2 stroke street motorcycles, they had tachs, but seems that wouldn't be a cheap solution
 

heligonka

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Aug 14, 2018
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what about those old 2 stroke street motorcycles, they had tachs, but seems that wouldn't be a cheap solution
Those old 2 stroke motorcycles had tachs alright, and they were mechanically driven by a tachometer cable from the tach drive gear in the engine to the instrument dial. That would not be of any use in the motorized bicycles.
 
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