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Cheap analog tach!

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I want to put an analog tach on my SM. I did a search, many people asked about an analog tach but there was never a good cheap solution. Until now! I bought a trick looking 2" tach off ebay.

Tach1.jpg

Tach2.jpg

Tach3.jpg

It's made by Timex, has a 10,000 rpm scale and a seven color backlite. It fits perfectly to the right of the speedo. The tach was only $23.99 but the guy charged me $15 shipping and it took over a month for him to ship it. :banghead:

Ok, now the down and dirty, how to get it to work on the thumper. It had a selector switch for 4, 6, or 3 cylinders (why three, I don't know). So I cut it open and traced the switch. Turns out the chip just looks for a 4-bit binary input, which means it will work on engines with 1 - 15 cylinders. That is very trick and super easy to change. Pin 10 = 1, pin 11 = 2, pin 12 = 4, pin 13 = 8. Just send power to any pin or combination of pins to tell it how many cylinders there are. To make it work on a 3 cylinder they sent power to pins 10 and 11 [1 + 2 = 3]. The DRZ has a waste spark system, which means it fires on the exhaust stroke in addition to the compression stroke, so you need to set the tach for 2 cylinders. Simple, just set the switch to 3 cylinders then break pin 10 off the chip so only pin 11 is getting power.

With that set, all that's left is to seal it up so it's waterproof. There is a button going through the lens. I just pulled it out, ditched the spring, and put it back in with an o-ring on either side of the lens. Water tight but the button no longer works so I soldered a wire to the switch and ran it out with the rest of the wires. Touching it to ground does the same thing as the switch. Now just glue the tach back together and glue up all the holes in the back. Bada-bing you now have a motorcycle tach.

I haven't mounted mine yet but I did buy a mounting cup from the auto parts store, $14.99. The bracket that came with it is big and ugly so I'll just make one that goes down to the bolts that hold the turn signal to the triple clamp.

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nice write up. as for 3 cylinders what's wrong with that? triumphs have triples and they are awesome motors. i love my Tiger and i think my next bike will be a Daytona 675. besides - 360 degrees of rotation divides nicely by 3 cylinders. aside from triumphs there are several super small economy cars that are triples, none of which are extraordinary really, but still.

be sure to post some pics of it on the dash!

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yah that looks like a sweet tach. Did you test the functionality yet? Where was it on ebay?

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Did you test the functionality yet?

It worked fine hooked to my function generator, haven't tried it on the motor yet. Mine reads a bit low but I didn't expect a cheap ass tach to be very accurate. It's actually pretty close.

Where was it on ebay?

ebay Tach

I don't recommend buying from him. It took him a month to contact me after I payed for it, and another two weeks til I actually had it.

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The DRZ has a waste spark system...

I did not know that. Why?

BTW: excellent analysis.

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Where will you connect the tach pick up wire (green wire)?

I plan to connect it to the coil primary wire, should work. If not I'll build an adapter.

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Yep. Geo Metro.

:banghead:

and the ever sassy subaru justy!

or better yet the foggy petronas superbike...

petronas.jpg

(photo by your's truly, 2004 wsbk)

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I plan to connect it to the coil primary wire, should work. If not I'll build an adapter.

the coil primary wire works. i have it on my tach. :banghead:

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if i get this tach too will someone help me install it. i'm not totally electicly challanged, i did all my aftermarket lights but i have no idea how to do this. :banghead:

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if i get this tach too will someone help me install it. i'm not totally electicly challanged, i did all my aftermarket lights but i have no idea how to do this. :banghead:

But your name is voltron!!!

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I did not know that. Why?

BTW: excellent analysis.

the timing is sensed off of the crank, it is a simpler system that way. it sparks on the intake strok and wastes a spark on the exhaust stroke.

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Finally got the tach on the bike. I haven't had any time to do it at home so I just brought it to work and did it there. Fits like a glove and looks like it belongs there.

Tach4.jpg

Tach5.jpg

I hooked the green wire to the coil primary and the needle doesn't budge. Gona have to build an adapter. May be a while, unless I can get it done at work. :applause:

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Looks sweet. Do you figure the adapter will fit internally? External Box?

will you make me one too ? :applause:

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Keep Going. Let us know how it works. I need one of these!!!!

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