Bike crank but wouldn't start.

[max]

From what you are measuring it appears you are correct, the circuit is open, the coil cannot "generate" the ac signal the ecu needs to determine at what time
the spark fires and also the fuel injection operation, it stops both functions.
These two are exactly the symptoms you have and as far as i can tell this is the only part on the bike that can cause this fault.
But like i said it only happens in very few cases, it seems a robust system that has to operate at hot temperatures that is not good
for the life of electronic parts so the coil is a good solution.

Here is what a reluctor sensor looks like inside;


1= the coil.
2= soft iron core.
3=permanent magnet.
If a ferrous metal moves past the tip of the sensor it generates an ac voltage as a result
of the magnetic field variation through the soft iron core

To verify if the ecu is ok you can measure the connector pin that would have the yellow wire in it.
in my case i measured 0.3 volts dc on it, you may measure a higher value but it shows
that the ecu is connected and the input is working, measured with the key on.

So if you are convinced that the coil is defective then you have to replace it, this coil is used on a wide variety of honda engines, but you need one that has the right type of connector, grommet with right angle rubber boot and correct length of cable to match your bike.

here is a picture of the page with the partnumber seven;



And a link to partsfish for that page, it has pricing and partnumbers;

https://www.partsfish.com/oemparts/a/hon...case-cover

And what it looks like without the cover and sensor;



It is not difficult to replace it and for someone like yourself that should be simple to do.
There is an opening in the lower crankcase as far as i can tell so maybe the oil is below that level when the bike is on the sidestand but i am not sure, the sight glass with the oil level suggests that
the oil is below the cover and there seems to be no gasket as a spare part.
So some type of silicone sealant appears to be required similat to what you did with the valve cover, maybe someone with a service manual can explain.

[GoldOxide_imp]

Great illustration share Max.

[Lord Popgun]

Max is correct. There is no gasket for the crankcase cover.

The specified sealant is Three Bond 1207 B or equivalent. Here is an Amazon link to it: [url=https://www.amazon.com/Three-Bond-Performance-Adhesion-Gasket/dp/B008BYPRRI/ref=sr_1_1?crid=2UL7H4Q8XGFEZ&keywords=threebond+1207&qid=1580335220&sprefix=Three+Bon%2Caps%2C159&sr=8-1]https://www.amazon.com/Three-Bond-Perfor...159&sr=8-1

Do not use silicone. It will not hold a seal. The manual specifies a specific place to put the sealant on the crankcase and then a full bead around the cover bypassing a certain spot at the top. This info is in section 17 of the service manual.

When removing the cover the engine oil will not drain out. A very small amount could be in there though.

There are 2 dowel pins. Don’t lose them and don’t forget to re-install them. Torque for the screws is not specified, just “tighten the bolts securely”. If that isn’t good enough for you, you have to use the standard torque values table in section 1 of the manual.

If you want to PM me a number I will take a quick picture of the pages and text them to you.
Max, regarding the CKP, there manual strangely doesn’t seem to bother checking coil resistance. Instead, they have the tech use a peak voltage tester. I didn’t google the part number to see what it looks like, but from reading the procedure it appears to be what the marine industry calls a DVA adapter (direct volt amp). They are available from CDI at least and are designed to plug into a Fluke meter. We use one a LOT at my friends boat shop.

You can google them. They only have 3 parts. A capacitor, a diode and a resistor. The cap has a fast charge time and slow discharge time. The diode does half wave rectification (IIRC) and the resistor provides a discharge path for the cap when you stop your test.

As the pulses occur, the cap charges until it reaches whatever value the pulses go to and you read it on the meter. The service manual says the value for ours is .7vdc minimum. And use a meter with impedance of 10Mohm/volt minimum.

The manual shows checking initially at the ECM connector. I’d consider removing the ECM connectors and reseating them first. Well, except in an above post the CKP coil appears to be open.

[zirconxi_imp]

Thanks for great the help Max and Popgun. I had called my area authorised honda sparepart and it seems its a rare item and they seldom stock it and need to preorder. I am thinking i might as well do some dissect on the cable to see if its broken somewhere while i wait.

[max]

Thanks for the info popgun, very precise, zirconxi you have a good look at that part, the first time i measured it i could not get a reading myself.
The contacts of the coil connector are a bit far into the plug housing and only after using some smaller probes was i able to read the 487 ohms.

There must be a lot of small wire in that sensor to produce 500 ohms.

If the sensor is actually broken that explains the problem, did you actually charge the 3 year old battery before the last test?

[zirconxi_imp]

I tested it with a new battery. Initially thought battery is the culprits, bought a new one to replace the 3 years old battery.

[SportsterDoc]

Max, validating your post 26, H-D Sportster CPK testing is very much the same:

Spοrtster crank position sensors are 2 wire units, which may be described as variable reluctance sensors or magnetic pulse gеnerators, etc. They do not have as clean a signal as hаll еffect, but generally more durable (simple coil). As with the hаll еffect, they are typically rated -40 C to 150 C (300F).

Note: This is a sine wave and requires the AC scale
While cranking: ~ 0.3 VAC
At idle: ~ 1 VAC
Static: N/A

Unfortunately, I did not retain the valuable info shared by Popgun, when we were analyzing idle issues.

[max]

Hi Doc, thanks for dropping in, i think zirconxi has a handle on it now, he did all the tests and provided he measured the coil voltage with his ac voltmeter that would indicate the rear occurrence of a broken coil.

He also measured a ( i think ) low ohms value from the white wire to ground which is correct so at least that conductor is fine, the bike ran ok up to that point so i don't think there is more than one fault at play here, i also found some info to support the diagnosis and help him understand the fault, it may also help someone else understand how this system works.

It can be a bit perplexing for some to see what role electrons play in our bikes and how they trundle around in our electrical system, so a little explanation could help here

Think i have read only one occurrence of such a coil failing, seems a reliable system and very easy to check once you understand what makes it tick.

[zirconxi_imp]

I had ordered a replacement sensor estimated to arrive in a month or so. Will know if the diagnosis is correct or other thing are causing the problem. Currently only this sensor are the suspect as there's no V reading from the sensor during cranking, and the sensor seems to have an open circuits.

[zirconxi_imp]

Hi Guys, do these crank sensor /pulse generator generally the same other than the connection cables?? It seems the CB650 pulse sensor look extremely alike other than the connecting cables and rubber bush slightly different. is there different spec for each Honda motorcycle model? or its just the connection different?