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I recently acquired a 1993 VFR750. Little rough, but good price and figured it'd be a nice project bike. I'll link the thread that the previous owner posted trying to figure it out, but basically he let it set for a couple years, and when he got back to it, the ugly starter clutch was problem arose. After he replaced it, it cranked over fine, but no spark. Since then the ICM and pulse gen coils have been replaced, and we have both been through all the troubleshooting in the manual, and still nothing. 

 

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  • 2 weeks later...

look at the wiring diagram and test that you get +12v to the black box when key and run switch are ON.  also test that the green wire there has zero resistance  to chassis.

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12 hours ago, squirrelman said:

look at the wiring diagram and test that you get +12v to the black box when key and run switch are ON.  also test that the green wire there has zero resistance  to chassis.

I’ve done that and it tests good, and the mechanic has gone through and not found anything wrong with the electricals. He said the only thing that seemed wrong with it was it sounded like the starter wasn’t turning it fast enough, and that could be why it wasn’t generating spark, but that doesn’t sound right. Hopefully he calls me back today or answers the phone at some point 

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5 hours ago, VFRedneck said:

Haven’t. Sat for a while, starter clutch went out, replaced it, no spark 

 

Wondering if I'm reading/interpreting this statement correctly?  I'm reading this as: The bike was running well, then had starter clutch problem which you fixed, and now it will not generate a spark.  If I was troubleshooting that scenario I'd start looking right were the last bit of maintenance was done, especially since the crankshaft-speed pulse generator hardware is located right there on the starter clutch.

 

Things like: are the two pulse generator sensors (variable reluctance sensors) that are located at the toothed-wheel portion of the VFR's starter clutch installed correctly?  not damaged?   are all the teeth (the little metal bumps that the pulse generator sensors are meant to read) on the perimeter of the starter clutch undamaged?  is the "air-gap" distance between the sensors and the teeth set correctly?

 

The bike's ignition control box won't command a spark if it doesn't receive a proper pattern of signals from the pulse generators.  The bracket holding the pulse sensors didn't get bent, did it?  Variable reluctance sensors are pretty sensitive to the "air-gap" distance between the sensor and the metal "teeth" spinning past on the perimeter of the starter clutch.  Also, a damaged tooth on the starter clutch perimeter might not be "read" correctly by the sensors.  

 

And... you said that you replaced the starter clutch, right?  Did you examine the replacement piece(s) to insure they were identical to the removed piece(s)?  I don't know if there was ever a difference in the pulse sensor tooth pattern on the perimeter of the starter clutch, but if there are 2 (or more) versions it's conceivable that you were accidentally supplied with the wrong one.

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8 hours ago, GreginDenver said:

 

Wondering if I'm reading/interpreting this statement correctly?  I'm reading this as: The bike was running well, then had starter clutch problem which you fixed, and now it will not generate a spark.  If I was troubleshooting that scenario I'd start looking right were the last bit of maintenance was done, especially since the crankshaft-speed pulse generator hardware is located right there on the starter clutch.

 

Things like: are the two pulse generator sensors (variable reluctance sensors) that are located at the toothed-wheel portion of the VFR's starter clutch installed correctly?  not damaged?   are all the teeth (the little metal bumps that the pulse generator sensors are meant to read) on the perimeter of the starter clutch undamaged?  is the "air-gap" distance between the sensors and the teeth set correctly?

 

The bike's ignition control box won't command a spark if it doesn't receive a proper pattern of signals from the pulse generators.  The bracket holding the pulse sensors didn't get bent, did it?  Variable reluctance sensors are pretty sensitive to the "air-gap" distance between the sensor and the metal "teeth" spinning past on the perimeter of the starter clutch.  Also, a damaged tooth on the starter clutch perimeter might not be "read" correctly by the sensors.  

 

And... you said that you replaced the starter clutch, right?  Did you examine the replacement piece(s) to insure they were identical to the removed piece(s)?  I don't know if there was ever a difference in the pulse sensor tooth pattern on the perimeter of the starter clutch, but if there are 2 (or more) versions it's conceivable that you were accidentally supplied with the wrong one.

Okay, that’s a lot of good information, and the thread I linked in the beginning was started by the previous owner who did the starter clutch repair. Since then I have inspected the starter clutch and the pickups, and saw that while the starter clutch had one bent tooth, but I just figured it’d still spark, but maybe it’d just run a little rough. Other than that, it seemed identical. I’m thinking that rather than the starter clutch job, it was the sitting that resulted in something going wrong. Hopefully tomorrow I can get the mechanic to answer his phone 

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8 hours ago, GreginDenver said:

 

Wondering if I'm reading/interpreting this statement correctly?  I'm reading this as: The bike was running well, then had starter clutch problem which you fixed, and now it will not generate a spark.  If I was troubleshooting that scenario I'd start looking right were the last bit of maintenance was done, especially since the crankshaft-speed pulse generator hardware is located right there on the starter clutch.

 

Things like: are the two pulse generator sensors (variable reluctance sensors) that are located at the toothed-wheel portion of the VFR's starter clutch installed correctly?  not damaged?   are all the teeth (the little metal bumps that the pulse generator sensors are meant to read) on the perimeter of the starter clutch undamaged?  is the "air-gap" distance between the sensors and the teeth set correctly?

 

The bike's ignition control box won't command a spark if it doesn't receive a proper pattern of signals from the pulse generators.  The bracket holding the pulse sensors didn't get bent, did it?  Variable reluctance sensors are pretty sensitive to the "air-gap" distance between the sensor and the metal "teeth" spinning past on the perimeter of the starter clutch.  Also, a damaged tooth on the starter clutch perimeter might not be "read" correctly by the sensors.  

 

And... you said that you replaced the starter clutch, right?  Did you examine the replacement piece(s) to insure they were identical to the removed piece(s)?  I don't know if there was ever a difference in the pulse sensor tooth pattern on the perimeter of the starter clutch, but if there are 2 (or more) versions it's conceivable that you were accidentally supplied with the wrong one.

Also there was a guy that had a thread showing the same issues as me, I think his name was nbogert, but he never listed what the fix was 

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On ‎10‎/‎10‎/‎2018 at 2:09 AM, VFRedneck said:

I’ve done that and it tests good, and the mechanic has gone through and not found anything wrong with the electricals. He said the only thing that seemed wrong with it was it sounded like the starter wasn’t turning it fast enough, and that could be why it wasn’t generating spark, but that doesn’t sound right. Hopefully he calls me back today or answers the phone at some point 

 

Hi VFRedneck.

Can't say I agree with your mechanic, if there's no spark how can it not be related to an electrical issue!

Ok, so back to basics. You say your battery is good, do you have good bonding of the battery Negative terminal to both Frame and Engine? Are you sure the ICM you replaced is serviceable and the Ignition Pulse Generators meet the Ohmic spec?

Have you verified your 4ea Ignition Coils are OK?

Other than that, and what others have suggested, use the diagram and verify EVERY wire from source to destination with an ohm meter. Verify you have the correct Ohm reading of the Ignition Pulse Generators AT the ICM. Make sure with Ignition switched to ON the 12v Supply is at the B/W wire AT the ICM and each of the 4 Ignition Coils.

Make sure every switch, fuse and the two diodes are all ok. Make sure the ICM Green ground wire is properly grounded (measured back to the Battery Neg terminal) Including grounds for Side Stand and Neutral Switches.

Hope this helps. Lets know what you find.

Good Luck.

 

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