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Tach inop

Old 07-03-2015, 10:59 AM
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Question Tach inop

I checked the wiring according to the S/M and the ground is perfect and on the Bk/Br I get 12V as I should. I've got perfect continuity on the Y/G wire which goes from the tach straight to the ECU with no shorts to ground. I do get some resistance to ground on the Y/G with the tach and/or ECU plugged in but I just attribute this to the signal going through the microchip on teh tach and through the ECU.Now I'm supposed to have 12V on this wire with the key and stop switch on according to the S/M and I'm getting exactly zero.


Does anyone know how I would/could test the tach to see if it's that or the ECU? I'm sure as hell not shelling out $500+ for a new ECU, I'll get an aftermarket set of gauges or just an a/m tach or something first lol.
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Old 07-03-2015, 01:17 PM
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Check fuse? Check circuit board for fried components on the tach? Sorry I dont have the schematic in front of me at the moment
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Old 07-03-2015, 01:31 PM
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Originally Posted by scottiemann View Post
Check fuse? Check circuit board for fried components on the tach? Sorry I dont have the schematic in front of me at the moment


Fuse is good and I pulled the tach assembly out of the gauge unit and the PCB looks fine, everything is in tact, nothing appears to be toasted, it all looks good.


I think it's the ECU honestly because I'm supposed to be getting 12V from the ECU to the tach on the Yellow/Green wire with the key and kill switch on according to the manual. However I get nothing at all - the meter just reads 0.00VDC. The Y/G wire only goes from the ECU to the tach, it doesn't branch off anywhere else. I do get continuity from the ECU connector (ECU unplugged) to the ring terminal that screws to the tach so I know the wire is good and there's no shorts to ground from the Y/G either so all that's left is the ECU I suppose.


If I was getting 12V at the tach and it wasn't working I'd say the tach.
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Old 07-03-2015, 04:59 PM
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do you have 12V getting to the ICU
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Old 07-03-2015, 05:02 PM
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I should because the bike runs. Everything works on the bike except the tach.
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Old 07-03-2015, 05:29 PM
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R/R failure?

my tach got fried as well as the ICU after an R/R failure about 4 years ago.. havent had a working tach since however with my current build I'm going to be running a universal tach ($65) and an ignitech programmable ICU ($200)
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Old 07-03-2015, 05:32 PM
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I don't think so but I'll check the output next time I fire it up. The guy I got it from had it for a year and he said it just stopped working one day. I have a universal tach that I'll probably use and just get a full Koso gauge set later on.
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Old 07-03-2015, 05:51 PM
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I'll be running a koso knock-off pics in my thread.

good thing about the universals the tach signal comes straight from the coil
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Old 07-05-2015, 09:37 AM
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OK so the r/r is fine - 14.2V at idle and doesn't go any higher. The front cylinder is intermittent at idle as evidenced by pipe temp. I'm thinking the ECU is toast - that may explain the irregular front cyl idle and no tach. I hooked a Koso tach to the front cyl and it seemed to drop out at the same time I could hear the front cyl drop out. eBay has a few ECU's for ~$60 shipped. I think I'll get one and see what happens. Does anyone know what the secondary CDI converter box does?

I also did the TPS setting and carb sync and that seems to have helped a lot.

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Old 07-05-2015, 10:31 AM
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As far as I know the CDI (capacitive discharge ignition) box is what tells the coils to fire... I could be wrong on that one but thats what I understand...
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Old 07-05-2015, 10:35 AM
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according to the wiring the ECU tells the secondary CDI converter to actually fire the coils, but the tach signal come straight from the main ECU on the Y/G wire
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Old 07-05-2015, 10:37 AM
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that is correct
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Old 07-09-2015, 10:06 AM
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Ok so I finally got to take it out for the first time yesterday and she runs MINT. Nice and strong, no lag, no hesitation. Still no tach and the front cyl dropping out at idle only. I'm aiming for the ECU at this point so I think I'll pick up one of the eBay units and see what happens as far as that goes.
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Old 07-09-2015, 10:34 AM
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I just did some peeking in the Tech forum and found someone else who said that their R/R fried and fried the ECU and they went with no tach until they got a new ECU so I'm betting on that.
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Old 08-14-2015, 03:20 PM
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Well I finally got an eBay ECU and still no go. Could be the ECU though. The guy I bought the bike from said the regulator went on him at one point. I'll double check the writing and voltages with this ECU tomorrow. I hope I didn't get a bum unit -_-
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Old 08-28-2015, 07:31 PM
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Well after doing some more poking around at the tach itself I found a blown diode on the PCB likely from when the regulator went. Because it was blown apart I couldn't get a value from it so I threw in a diode I had around and then the resistor connected to that diode went up in smoke - I guess it was the wrong value lol. Oh well it's not like the tach worked anyways. I'm going to order up a set of gauges from eBay and just pull the tach unit out of them
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Old 08-28-2015, 10:08 PM
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When my tach went out it was the ecu. Got an ebay one and all was good. Sorry to hear it didn't work.
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Old 08-29-2015, 06:23 AM
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Originally Posted by smokinjoe73 View Post
When my tach went out it was the ecu. Got an ebay one and all was good. Sorry to hear it didn't work.


Yea I think it was your post that I saw that on so that's the route I went because this one had the regulator go out as well. Oh well. The seller is taking the ECU back so that $60 will go towards a gauge set.
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Old 08-29-2015, 07:28 AM
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Before I did the ecu, I ran an aftermarket tach for months. Then a koso knock off, then the CBR600RR dash.

Keep posting on how it goes.
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Old 08-29-2015, 07:47 AM
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Originally Posted by smokinjoe73 View Post
Before I did the ecu, I ran an aftermarket tach for months. Then a koso knock off, then the CBR600RR dash.

Keep posting on how it goes.


Yea I've got a small round Koso tach that I can use if need be but I'd rather not go through the trouble of wiring it all up just to pull it back out when I get a replacement tach lol.
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Old 09-09-2015, 11:57 AM
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So I gambled on a set of busted up gauges on eBay for $30. Basically everything was wrecked EXCEPT the tach. I swapped teh tach into my gauges today and it works great! Finally!
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