cheapo chinese tach test By glavey (Read 1,892 times)

[glavey]

This won't be an in depth test or review, I just wanted to let people who are looking at these know they do work.

I have wanted an analog tach on my scoot for a while so when I had a few extra dollars around I decided to venture onto the interwebs and see what I could find.

If you look around amazon or ebay for a motorcycle or scooter tachometer chances are very good you will find a tach that looks similar to this one.

I ordered that tach a few weeks ago and just recently had a chance to try it out on my scoot.

Before I get to the results, I'll go through the wiring. It's quite easy; connect the black wire to switched +12v, green to ground, and yellow/black to the positive side of your ignition coil. The orange and blue wires go to the light so their polarity doesn't really matter, just connect one to switched +12v and the other to ground.

When I tested the tach, I was just seeing if it worked so I used a very quick and dirty wiring job involving many alligator clip test leads.

With the engine running the tach read very close to what my other digital chinese tiny-tach knockoff read. At about 4000 rpms the reading was about 100 rpms off as compared to the tiny tach, at 6000 rpms it was off by about 250 rpms.

The needle movement is not very fast, nothing like you get in a car. if you quickly revved the engine to 6krpm from idle, it might take the tach about 1/2 to 3/4 seconds to get to the 6k mark.

Here is a video from youtube that shows the same type of tach and a real tiny tach connected to an engine for comparison. Note that this is not my video.

[LUKE]

omg, is that a lawnmower?
where is that tach made from? china or non china?

nice video

[jct842]

The video is not very relevant to your testing since it isn"t yours and we don't know how it was hooked up.

[glavey]

Very true. If I can I'll get a video comparing the two tachs on my scooter. I will give an advance warning though; the digital tach in my scoot only reads 1/2 on the actual rpms, I think it was designed for a 2-cylinder engine.

The tach (the one linked to in the OP) is made in and ships from china.

[Bashan]

Thanks Glavey, nice write up. The analogs are never as fast but there's something about that needle sweeping around that makes it easier for me to use. You don't have to look at a number and think what it means. With analog you know what position the redline sits at and when it gets near there, well, you're near there. Rich

[glavey]

I know precisely what you mean. It's like analog vs digital watches.

I want to work on building an analog tach from the stepper motors from GM dashes and an arduino. I would imagine those would be lightning quick.

Edit: One additional thing I should add is that the wires coming from the tach are an incredibly small gauge. It wouldn't surprise me if the cross-section of the wires were less than 0.75mm. The insulation makes them look like 18-16 gauge, but the wire inside is much smaller. I would suggest soldering, not crimping, on a bigger wire and then wire the tach into your scoot from those wires.

Also, the rubber instrument light holder is, well... clumsy is the best way I can put it. There are folded metal contacts inside of a rubber boot. The contacts are not adhered in any way to the rubber, they just sit in cut out corners. The light bulb itself looks to be a rather rare one. I'll get pictures of all of this tomorrow.  

[rks]

Jul 13, 2014 16:01:34 GMT -6 glavey said:

Very true. If I can I'll get a video comparing the two tachs on my scooter. I will give an advance warning though; the digital tach in my scoot only reads 1/2 on the actual rpms, I think it was designed for a 2-cylinder engine.

The tach (the one linked to in the OP) is made in and ships from china.

I'll bet that your digital tach can be set to read correctly on your scooter...I bought this one over 2 years ago...made in China...sold thru Ebay...$12.59 including shipping....still works fine, and can be set for 1 or 2 cylinder engines...Bob

[img src="i1271.photobucket.com/albums/jj622/rks3526/KGrHqJHJBYFBUdNooEcBRrQezWhg60_12.jpg" src="" alt=" "]

[glavey]

Mine doesn't have any buttons. It is just a plastic case with a potted back and a channel for the wire to slide in to.

Edit: Here is a quick and dirty video showing the digital and analog gauges together. They were off by more than I remember, but keep in mind we are essentially comparing one chinese tach to another chinese tach