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Old August 10th, 2017, 09:13 AM   #15
DannoXYZ
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Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011

Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C

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MOTY - 2018, MOTM - Nov '17
Quote:
Originally Posted by Flying View Post
I had a similar problem and am inclined to say its a problem with the wiring harness. Is the neutral light working?
Quote:
Originally Posted by gitter View Post
As far as lights, neutral, oil, temp, blinker and the back lighting to all the gauges works. The needles on the tach and gas gauge don't seem to be working. (Also the no spark thing)
Gauges dying at same time is clue, I bet black signal wire between ECU and coil is shorting out with some of gauge wires. The tach gets its RPM signal from left-coil black wire. They all share common power and ground wires. Let's test black signal wire between ECU and coil.

1. Unplug connector from ECU and black wire from coil. Measure resistance of black wire from end-to-end.

2. Measure resistance of black wire from either end to chassis ground.

These tests will at least tell us health of signal wire to left coil. Now, signal on that wire should look like this:



Unlike popular misconception, ECU/ignitor does not send power to coil to fire plugs. Coil is powered fulltime directly from battery through ignition/kill-switch, and ECU/ignitor grounds coil to fire plugs. So oscilloscope trace you see is signal on green (right) or black (left) wire between ECU and coils. During spark OFF time, coil is charged from other side by red +12v wire. Since signal side is open (disconnected), there's no current-flow and no voltage-drop; we see battery voltage on both sides of coil. Then during spark ON time, ignitor grounds green and black signal wire to dump coil and fires plugs.Those are momentary dips to zero you see on trace.

With oscilloscope, we just test for this signal at ECU-ignitor socket. Then work forwards on green|black wire towards coils to see if it stops somewhere due to broken wire or bad connector. Where signal disappears is your problem. Without oscilloscope, you can use 'noid-light. Gives you binary ON/OFF data instead of nice 'scope trace, but serves same function.

So test resistance of black signal wire for now. And get 'noid-light. I'll look up how to test gauge and fuel-level wires; I suspect these failures are all connected...

Last futzed with by DannoXYZ; August 10th, 2017 at 09:51 PM.
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