Author Topic: (Solved) Bare bones wiring, still no spark  (Read 706 times)

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Offline JWB

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(Solved) Bare bones wiring, still no spark
« on: May 22, 2020, 10:27:53 AM »
My first project bike, 74 550, was purchased with much of the electrical parts missing and the wiring a cut and spliced mess.  New parts are: main and sub wiring harnesses, solenoid, rectifier, fuse box, ignition starter switch, ignition coils(with wires),  and plugs.  Got all my parts, hooked them up an nothing, not a light, button anywhere that worked.
Using a video I found on Classic Octane as a reference, I did the following to troubleshoot at the most basic level. I disconnected everything, direct wired the yellow wire from the points to the coil for cylinders 2 & 3, blue to the coil for 1 & 4, connected both b\w coil wires to the positive side of the battery, connected the + and - sides of the solenoid, then connected the  y\r and black wires from the solenoid to the battery to kick in the starter.  Starter works just fine but no spark.  I pulled a plug and grounded it against various surfaces, but still no spark.
Am I missing something or should I get spark?  What do I check now?
« Last Edit: May 23, 2020, 07:20:14 PM by JWB »

Offline tlbranth

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Re: Bare bones wiring, still no spark
« Reply #1 on: May 22, 2020, 10:58:40 AM »
with the points (either one) open and ignition on, check the voltage between the points post and ground. If not 12v or so your power is not reaching the points or the post is grounded or the condenser is shorted. That'd be a place to start.
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Offline bryanj

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Re: Bare bones wiring, still no spark
« Reply #2 on: May 22, 2020, 11:13:28 AM »
Points wires not assembled correctly
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Offline Deltarider

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Re: Bare bones wiring, still no spark
« Reply #3 on: May 22, 2020, 11:56:23 AM »
Please specify what Classic Octane video. I've watched quite a few of these self proclaimed experts demonstrating how to do the timing of the ignition, as proud as a horse with two dicks. Was that the video where he forgot to mention you have to check the breakerspoint gap first?*
* where BTW most off timing originates
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Offline JWB

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Re: Bare bones wiring, still no spark
« Reply #4 on: May 22, 2020, 12:23:10 PM »
The video is titled, "Running a Honda CB500 engine on the engine stand"
Checked the post side of open points to a grounded point on the frame and it shows 12v, so that is good.
Forgot to mention the coils are bolted to the frame so they are grounded.
When assembling the new spark plug caps to the coil wires I might have messed up, so perhaps I should check those.
Using a multi-meter can I check if voltage is getting that far?  If so how, and what am I looking for?

Offline tlbranth

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Re: Bare bones wiring, still no spark
« Reply #5 on: May 23, 2020, 05:23:05 PM »
So your primary circuit appears to be correct. With the multimeter set to ohms, read from #1 plug cap to #4 plug cap and then from #2 to #3. You should see about 10k ohms (I think). If you see no meter movement there's a plug wire, plug cap or coil secondary problem.
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Offline scottly

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Re: Bare bones wiring, still no spark
« Reply #6 on: May 23, 2020, 05:44:32 PM »

Checked the post side of open points to a grounded point on the frame and it shows 12v, so that is good.

Now rotate the motor until the points are closed; the voltage should drop to Zero.
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Offline JWB

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(Solved) Bare bones wiring, still no spark
« Reply #7 on: May 23, 2020, 07:19:34 PM »
You all came through again!  I was the points after all, at least one set, not both.  Dummy me only was checking the #4 plug since it is on the outside and then only checked one set of points which were working correctly.  I pulled #3 and what do you know, there was spark.  Then I checked the other set of points and noticed that they were not opening at all.  Duh me.
Now to learn how to set the points correctly.
Thanks again, y'all.
John

Offline tlbranth

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Re: (Solved) Bare bones wiring, still no spark
« Reply #8 on: May 24, 2020, 09:16:55 AM »
Glad you found it. Always best to go back to basics.
Don't own a Vanagon
Don't work at Boeing
Life is good

1970 CB750 K0
1975 GL1000
1999 GL1500
2002 VT750-CDA ACE - Momma's bike
Terry

Offline Deltarider

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Re: Bare bones wiring, still no spark
« Reply #9 on: May 24, 2020, 12:42:58 PM »
... With the multimeter set to ohms, read from #1 plug cap to #4 plug cap and then from #2 to #3. You should see about 10k ohms (I think)...
Actually it will be more like 14-15kΩ for the coil secundary circuit plus the resistance the caps may have, usually 5-7kΩ each. So, coil secundary and both plugcaps in total may give a reading of 24-29kΩ.
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