Resistance

[Festus]

In my ever loving quest to never give up learning FJR tech, I have a coil question for Gen 3 coils and injectors.

In the manual, it says if you measure the ohms between the two pins on a coil that it should measure between 1.19/1.61. If the coils are measuring 2 ohms on that reading, it indicates they have more resistance than Yamaha says they should have. More resistance, in theory, means a weaker spark.

Are coils measuring 2 ohms bad?

I'm talking primary resistance, not secondary (haven't gotten that far yet).

Moving on, Mama Yama says the resistance on fuel injectors should be 12. Doesn't give a range. Just says 12. If you have injectors reading 13.9, would that cause you concern? Again, most resistance, in theory, means a weaker injector.

[FJRoss]

And how accurate do you expect your ohmmeter to be at 2 Ohms? Don't think I would worry about it.

[Festus]

And how accurate do you expect your ohmmeter to be at 2 Ohms? Don't think I would worry about it.

No idea I'm an electrical vacuum

[raYzerman]

Close counts in horseshoes, in this case... what you don't want to find is an open circuit (very little or no resistance) or a short (infinite resistance).... give it some tolerance, i.e., 2 ohms is fine.

[Festus]

The oscilloscope on the coils looks good. It was just something I was checking while the hood was up, so to speak. Was there, why not check it all? Now I know.

[Red]

The oscilloscope on the coils looks good. It was just something I was checking while the hood was up, so to speak. Was there, why not check it all? Now I know.

Festus,

I'd be curious to see what the O-scope showed you on the coils. Pix welcome.

If your O-scope has the X/Y function (may be in the manual), I could go you one better, if you want more information from your components. You can buy or build an Octopus (Curve Tracer). Simpler versions are probably better, for motorcycle work. The options on commercial Curve Tracers are more for diving deep into the guts of a circuit board, rather than bike ignition issues.

Here is the simplest Octopus I know. Start with an orphaned wall-wart power supply, 6 Vac or so, as the transformer power source. The wall-wart will have the output Voltage listed on the face. Don't use a DC power supply, here. Two Voltmeter probes, two coax jacks, and a few resistors will do the deed, in any plastic box. You can use stand-off posts or a terminal strip to mount the resistors, if you have an OCD episode.

https://www.qsl.net/kd7rem/img/test/octopus.gif
The Internet will show you the various results (O-scope displays) for coils, capacitors, diodes, et c. You probably won't gain much if you try the Octopus on circuit boards, unless you have a known good (identical) circuit board to compare the bad board against.

[Bounce]

We are Dyslexics of Borg. Resisters are fertile. Prepare to be asslaminated.

[SkooterG]

Close counts in horseshoes, in this case... what you don't want to find is an open circuit (very little or no resistance) or a short (infinite resistance).... give it some tolerance, i.e., 2 ohms is fine.

Am I a complete idjit? Or did you mix the two up?

[Festus]

I'd be curious to see what the O-scope showed you on the coils. Pix welcome.

Here ya go. I'm sure I didn't have everything set for the best possible output to the screen, but it served it's purpose to me. I now know that there is no problem with the ECU/coil process. From what I have seen in my learning is when an ECU has issues with the spark, it shows up here. I got no signs of anything in that arena, so from a troubleshooting method, I've ruled out the ECU/Coils. I didn't think it was that, but since the hood was up, might as well take 5 minutes and check and now we have the data.


Coil 1




Coil 2




Coil 3




Coil 4

[Red]

Festus,

Thanks. Just wanted to add, the Octopus provides all the power needed, when you test any part. Turn off all other power to the unit being tested. The Octopus can test a coil or diode (or anything else) as you hold it in your hand. In circuit, some other components can "add" to the expected Octopus display on the O-scope.
On the O-scope, a coil will look like 0 and a diode will look like L on the screen. A straight line on the screen for either part shows you have a bad component.
When these components are connected in circuit, a coil with a diode may look like 0_ on the screen.

[Festus]

Red, thanks for that. I specifically wanted to test them in the bike to eliminate the ECU as a fault path. I'll look into the octopus. Might be something useful down the road.

[dcarver]

Festus, that spark pattern looks great!

[Festus]

Festus, that spark pattern looks great!

Thanks! I feel like I'm actually learning to troubleshoot rather than just throwing parts at things.