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Discussion Starter · #1 ·
My bike was stolen last year and I am very lucky to get it back. Whoever had the bike broke the ignition switch to unlock it and hot wired it. The thief left a gas station receipt in the cargo compartment from two days before the bike was recovered, so he must had been riding it.

I haven’t been able to start the bike yet.

What I have done so far:
  • Replaced the ignition switch
  • Replaced the main fuse

Now the lights, the horn etc get power when the switch is turned on. I can also hear the fuel pump priming. There is some engine error code but I think it is due to disconnected head lamp from some other posts. When I try to start the engine, it rotates but won’t start. I think there is no spark. I measured the voltage across the ignition coil and the ground with a multimeter when and there is no reading. I am not sure what I need to do next. Any recommendation and guidance is appreciated.
 

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You sound like you know what you're doing, but so often we discount the obvious.
Your description sounds identical to so many I've read here over the past 10 years.
Many, if not most, of these non-starting woes were caused by the battery having enough power to run accessories and start the fuel pump, but not enough to actually start the bike.
 

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Is the ignition switch an OEM unit?

I believe the OEM ignition switch has a resistor that the aftermarket switches don't. Without the resistor, it will crank but not start. I had also heard something about the ECU being matched to the ignition, but don't know the details. A Honda dealer should be able to tell you if there is a procedure that needs to be done to mate the new ignition - if it's necessary.

The lack of a resistor is the most common issue when people replace the ignition switch with an aftermarket one.
 

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no power at ignition coils shows break somewhere between ignition-switch to kill-switch to ignition coils. Measure voltage at following locations (follow path of electricity):

1. battery voltage = ?
2. voltage going into ignition-switch
3. voltage coming out of ignition-switch with key ON
4. voltage going into kill switch
5. power leaving kill switch (switch = run)
6. voltage going into ignition coils

Where power disappears shows problem between there and last location tested.
 

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Discussion Starter · #7 ·
You sound like you know what you're doing, but so often we discount the obvious.
Your description sounds identical to so many I've read here over the past 10 years.
Many, if not most, of these non-starting woes were caused by the battery having enough power to run accessories and start the fuel pump, but not enough to actually start the bike.
Thanks. I forgot to mention that the battery was fully charged with about 12.7 volts.
 

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Thanks. I forgot to mention that the battery was fully charged with about 12.7 volts.
That's a good start, but a battery needs to be tested under load to know if it's good or not.

Easiest way to do that is to read the voltage as it's cranking over. It should still hold over 10V during cranking. Some will show full charge (12.7V) before cranking, then drop to 6V or less under load, then come back to reading normal voltage.
 

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Discussion Starter · #10 ·
Is the ignition switch an OEM unit?

I believe the OEM ignition switch has a resistor that the aftermarket switches don't. Without the resistor, it will crank but not start. I had also heard something about the ECU being matched to the ignition, but don't know the details. A Honda dealer should be able to tell you if there is a procedure that needs to be done to mate the new ignition - if it's necessary.

The lack of a resistor is the most common issue when people replace the ignition switch with an aftermarket one.
Thank you. The new ignition switch is aftermarket from eBay. Do you remember where you saw the information about the resistor? I haven’t found anything helpful yet. Also I don’t understand what the resistor does in the circuit. I can get a resistor from work and wire it if I know its value and location.

And the battery is good. It is over 11 V while the engine is cranking.
 

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Discussion Starter · #11 ·
no power at ignition coils shows break somewhere between ignition-switch to kill-switch to ignition coils. Measure voltage at following locations (follow path of electricity):

1. battery voltage = ?
2. voltage going into ignition-switch
3. voltage coming out of ignition-switch with key ON
4. voltage going into kill switch
5. power leaving kill switch (switch = run)
6. voltage going into ignition coils

Where power disappears shows problem between there and last location tested.
Thank you. I looked at everything you listed.

1. Battery voltage: 12.3 V
2. Voltage going into ignition: same as battery
3. Voltage coming out of ignition with key ON: same as battery
4, 5. Voltage into and leaving kill switch: I am not sure where the leads are, but the fuel pump primes when the kill switch is turn on.
6. Voltage into the ignition coil: same as battery
 

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Thank you. I looked at everything you listed.

1. Battery voltage: 12.3 V
2. Voltage going into ignition: same as battery
3. Voltage coming out of ignition with key ON: same as battery
4, 5. Voltage into and leaving kill switch: I am not sure where the leads are, but the fuel pump primes when the kill switch is turn on.
6. Voltage into the ignition coil: same as battery
OK, we're making good progress. This is better than your earlier condition.

I measured the voltage across the ignition coil and the ground with a multimeter when and there is no reading.
 

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Thank you. The new ignition switch is aftermarket from eBay. Do you remember where you saw the information about the resistor? I haven’t found anything helpful yet. Also I don’t understand what the resistor does in the circuit. I can get a resistor from work and wire it if I know its value and location.

And the battery is good. It is over 11 V while the engine is cranking.
It's actually a 5v zener diode in ignition switch as theft-deterrent to prevent hot-wiring bike. It goes in between supply line at ignition-switch and pink wire going to ECU. In reverse-bias direction, it reduces voltage to about 9v. This is how ECU knows proper ignition-switch and key is used rather than hot-wiring which sends full-battery voltage to ECU's pink wire.

There's pictures of zener diode in this thread: Honda cbr250r No spark

Note guy has zener diode installed backwards and it doesn't reduce voltage going to ECU, which thinks it's being hot-wired and refuses to start bike. I posted photo with correct reverse-bias orientation of diode.
 

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Discussion Starter · #14 ·
OK, we're making good progress. This is better than your earlier condition.
Actually I haven’t had any progress since last night. I think I didn’t get any voltage reading at the coil because the multimeter lead wasn’t touching the metal part.

Today I tried cranking the engine while holding the ignition coil next to the bike frame. There’d be some arc between the coil and the frame if everything goes right. And there was nothing.
 

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Discussion Starter · #15 ·
It's actually a 5v zener diode in ignition switch as theft-deterrent to prevent hot-wiring bike. It goes in between supply line at ignition-switch and pink wire going to ECU. In reverse-bias direction, it reduces voltage to about 9v. This is how ECU knows proper ignition-switch and key is used rather than hot-wiring which sends full-battery voltage to ECU's pink wire.

There's pictures of zener diode in this thread: Honda cbr250r No spark

Note guy has zener diode installed backwards and it doesn't reduce voltage going to ECU, which thinks it's being hot-wired and refuses to start bike. I posted photo with correct reverse-bias orientation of diode.
I have actually seen that post but thought it was irrelevant lol. I am going to take a look tomorrow. But I won’t have much time to work on the bike until next week. Drill weekend.
 

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Danno is The Man with the answers to complicated electrical problems!

Pretty sure that the ebay switch, and lack of resistor, is the problem.
 

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Discussion Starter · #17 ·
I am going to take off the new ignition switch when I am free and see if there is this diode. If not, I will put the diode from the old switch on the new switch.
 

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Discussion Starter · #18 ·
It's actually a 5v zener diode in ignition switch as theft-deterrent to prevent hot-wiring bike. It goes in between supply line at ignition-switch and pink wire going to ECU. In reverse-bias direction, it reduces voltage to about 9v. This is how ECU knows proper ignition-switch and key is used rather than hot-wiring which sends full-battery voltage to ECU's pink wire.

There's pictures of zener diode in this thread: Honda cbr250r No spark

Note guy has zener diode installed backwards and it doesn't reduce voltage going to ECU, which thinks it's being hot-wired and refuses to start bike. I posted photo with correct reverse-bias orientation of diode.
44712

I think you are right. The new switch doesn’t have a diode.
 

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Seem to be missing pink wire as well. Best solution is to remove wiring-harness and diode from old ign-switch and solder them to new one.
 

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Went through this with an auction theft recovery bike. I bought a pack of 10 Zener diodes for a few bucks. Let me look around and I will mail them to you. Then you can help others out in the future! My understanding is the diode backs the power down from 12.7 to 9 volts for a "handshake" to allow starting. After 2 weeks of screwing around with an ebay ignition it was awesome to have the bike fire right up with a diode equipped key switch.
 
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