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Author Topic: Coil Grounding  (Read 6665 times)

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Offline Prospect

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Coil Grounding
« on: August 19, 2012, 03:42:40 PM »
Are the coils grounded to the frame via the two metal mounts or is it via the black wire?  I'm trying to diagnose a possible coil issue.  Bike is a cb750k1
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Offline killersoundz

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Re: Coil Grounding
« Reply #1 on: August 19, 2012, 03:44:21 PM »
Nope they don't get grounded. The plugs ground out to the engine.
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bollingball

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Re: Coil Grounding
« Reply #2 on: August 19, 2012, 03:53:23 PM »
+1 They can hang in the air or be rubber mounted ;D
Ken
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Offline TwoTired

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Re: Coil Grounding
« Reply #3 on: August 19, 2012, 04:09:15 PM »
1- coils need no frame ground
2- Black wires on these Hondas are NOT Ground.  Black wires in the harness are switched +12V.  Harness Grounds are green.
It's in the FAQ, as well as a wire diagram for the bike.

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Lloyd... (SOHC4 #11 Original Mail List)
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Offline Prospect

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Re: Coil Grounding
« Reply #4 on: August 19, 2012, 04:58:55 PM »
ok thanks. 
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Current Bikes

1969 CB750  Sandcast #256
1971 CB750K1
1972 CB750K1
1975 CB400F
1975 GL1000 Goldwing
1954 Harley Davidson Panhead
1957 Harley Davidson Panhead

Toronto Canada

Offline scottly

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Re: Coil Grounding
« Reply #5 on: August 19, 2012, 06:56:42 PM »
The main harness green wire is grounded on one of the coil mounting bolts. The coils themselves are "grounded" thru the points, via the blue and yellow wires. ;)
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Offline Raul CB750K1

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Re: Coil Grounding
« Reply #6 on: August 20, 2012, 07:29:30 AM »
All the above is true

BUT

if the condensors are located at the coil bracket, you need it grounded.

I commited that mistake. Painted the frame and thought no ground was necessary. My CB350 run like crap.

It took me a lot of "not seeing the forest because of the trees" to realize that without the condensor grounded, the spark was not strong enough. Wire-wheeled the frame at the bracket bolt, and the bike run well again.

Can't remember where does the fours have the condensors. They coul be at the points plate but I dont' remember, it's been years since I don't have to adjust my CB750 points. If such is the case, then you don't need ground at the coils bracket.
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Offline CycleRanger

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Re: Coil Grounding
« Reply #7 on: November 24, 2012, 11:31:54 AM »
Quote from: Raul CB750K1 on August 20, 2012, 07:29:30 AM
All the above is true
BUT
if the condensers are located at the coil bracket, you need it grounded.
I committed that mistake. Painted the frame and thought no ground was necessary. My CB350 ran like crap.

Just the information I was looking for.
The forum provides... :)
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Offline Xnavylfr

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Re: Coil Grounding
« Reply #8 on: November 24, 2012, 12:27:09 PM »
Another thing to add, Make sure when you install new points you have the phenolic washers BETWEEN the wires and connection post or it will ground out and NO SPARKY>>


Xnavylfr(CHUCK)
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Offline TwoTired

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Re: Coil Grounding
« Reply #9 on: November 24, 2012, 02:31:49 PM »
While the coils don't need grounding, the condensers do.
However, it would be extraordinary for the SOHC4 condensers to NOT be grounded, as they are located on the points plate.  If the plate isn't attached to the engine block (ground), the points won't function either.

If you painted the points "pocket" in the engine block and points plate mount posts, then the three mount screws need to make ground path.

You will need a good ground path between battery NEG and the engine case, as well, with no paint insulators.
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline TwoTired

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Re: Coil Grounding
« Reply #10 on: November 24, 2012, 06:18:43 PM »
Quote from: rotortiller on November 24, 2012, 02:44:54 PM
Quote
The main harness green wire is grounded on one of the coil mounting bolts.

The transformer core is grounded.

True, but that is a mechanical mount feature.  It is not required for proper operation.
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline TwoTired

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Re: Coil Grounding
« Reply #11 on: November 24, 2012, 07:58:44 PM »
no.  Nothing informative or very clear at all, really.

Certainly nothing to help understand what is needed for function.
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

bollingball

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Re: Coil Grounding
« Reply #12 on: November 25, 2012, 11:56:58 AM »
Quote from: rotortiller on November 24, 2012, 07:24:12 PM
Did I say it was needed for proper operation?

rt

No you did not. Which makes me wonder why did you bring it up at all?

Quote from: Prospect on August 19, 2012, 03:42:40 PM
Are the coils grounded to the frame via the two metal mounts or is it via the black wire?  I'm trying to diagnose a possible coil issue.  Bike is a cb750k1

It is clear that he has an electrical problem and needs to know if the (transformer core) needs to be grounded. Then you come back and say it is grounded. That could confuse a person trying to understand how this works. It would have been better to say it is grounded but does not need to be. Just saying ;)
Ken
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