Topic: 1974 CB550 No Spark

[Spanner 1]

The solenoid would only 'click' with an 11V battery  ....... Heatwave, Les?... it's 30 C here 

[LesterPiglet]

A heatwave here is anything 20 or above. I had to take off my overcoat.

[Spanner 1]

Actually will top-out @ 35 C today  ... and 10 of us are going for a 160 mile ride... airflow jacket and plan a route with zero traffic stops and it's not too bad ...

[shade]

The Kill switch is in the correct position but the starter button is now all messed up.  It was in bad shape to begin with and when I opened it up the starter button just fell apart.  However the kill switch is still intact and I can manipulate the starter button too work.

There was also some kind of kill switch added to the bike I think, I try it in both positions but maybe it is just broken?

[LesterPiglet]

I thought you had removed that switch. 

[TwoTired]

Buzz upon stater activation:  Cause: voltage variation at the buzz frequency.

The solenoid's function is to drop a big shorting bar across two hefty internal contacts, which serves to connect the battery to the starter motor.
The big bar is physically connected to a metal slug that slides inside a coil of wire.  The coil and slug form an electromagnet.  Pressing the starter button energizes the electromagnet, which moves the slug and thus the bar across the big contacts.  The bar is held across the contacts with the strength of the electromagnet, which is directly related to the voltage applied to the solenoid electromagnet.  If the voltage applied to the electromagnet becomes weak, the shorting bar disengages.  If the voltage pulses, the shorting bar pulses and it makes a buzzing sound.

What makes the voltage vary at the buzz frequency?  Whenever load or demand on the battery exceeds capability.

The starter motor presents more electrical demand than does the entire rest of bike. Instantaneously doubling or tripling the load on the battery.
A weak battery cannot sustain such a load and the voltage drops when the solenoid engages.  The voltage drop lowers the solenoid activation voltage and it releases the shorting bar, removing the load from the battery.  The voltage rises and the solenoid re-engages the starter motor. The load again drops the voltage and the cycle, oscillation, or buzz continues until there is no voltage delivered to the solenoid.

It should be noted that even a good strong battery can be forced into solenoid buzz with a starter motor defect.  A defect which causes the motor to draw far more than normal current for operation, can exceed the battery's ability to deliver.  Essentially, even a good strong battery behaves as a weak one when the current demand is too great.  The same voltage drop occurs and the solenoid again buzzes.  Different root cause, but the same buzzing sounds.

A third cause of solenoid buzz is borderline voltage delivery to the solenoid activation coil.  If the distribution path between battery and solenoid have in line voltage losses, the solenoid's activation is weakened, and the added current load from the starter motor can drop the activation voltage below solid hold-in levels for the solenoid.  Again a buzz can occur.

In the context of this thread, a weak battery can also cause spark issues.  And an 11 volt battery reading indicates a weak, depleted battery.

[bollingball]

The big bar is physically connected to a metal slug that slides inside a coil of wire.  The coil and slug form an electromagnet. 

I wonder if that slug is laminated? I have heard them buzz when they delaminate. But I don't know if the Honda ones are or not.

Ken

[iron_worker]

If the battery really is 11V it could be clicking the solenoid on and then the rush of current to the starter further drops the voltage ... which releases the bar... then the voltage picks up again and the bar contacts again, etc.

Repeat that cycle very quickly and it could make a buzzing sound?

Or could just be the humming of the starter motor trying to turn but not having enough power.

Low battery could also be why you have no spark! Charge your batt!

IW

[shade]

Thank you all for the information and help.

I charged the battery all day yesterday, and i removed the kill switch on the side of the bike and re-connected the wires that ran to it.  I will try another spark test later today.


Thanks

[shade]

Still no spark.
The battery is reading around 13, and when I touched the black wire to the negative terminal on the battery and the red to the metal piece  inside the starter switch and it reads 11.58.  Does this mean anything?

[TwoTired]

Insert slim paper/cardboard between both point contacts.

Turn the lights off at the bars.

Stop RUN Stop switch set to RUN.

Key switch on.

A) - One probe on battery NEG terminal.  The other probe on the yellow and blue (in turn) connection to the points.  Note readings and report.

Remove paper and carb board.

Rotate the engine crankshaft so that one set of points is closed.
B) - Measure ether yellow or blue connection of the selected points set that is closed.  Note reading and report.
Rotate crankshaft so that the other opposite point set is closed.
C) - Measure ether yellow or blue connection of the selected points set that is closed.  Note reading and report.

D) - Measure the voltage at the battery posts.  Note reading and report.

Post findings for the next step.

[shade]

Battery Reading 12.94

With cardboard between both points:
Blue: .80
Yellow: .22

Cardboard removed:
Blue Points Closed: .80
Yellow Points Closed: 0

[TwoTired]

Ok, power isn't getting the coils
Trace the power back to the source.

Find the  Black/white to the coils. What is voltage there with key switch and stop-run-stop switch in run position?

If still no voltage there, find the black wire that feeds the stop-run-stop and check the voltage to it.

This is what the wire diagram is for.  A map to follow the electron roadway about the bike.  You can read a map, right?


Blue points should read Zero when closed.  You may have to file off the film coating on their contact surfaces.

[shade]

Thanks for the help TwoTired.
I can read a map, but I cannot read the wiring diagram.  It makes no sense to me.  I already tried to follow the wires from the points into the rest of the bike, but they just join up with the larger cluster of wires. 
Not sure what I can do to resolve this.

[TwoTired]

I already tried to follow the wires from the points into the rest of the bike, but they just join up with the larger cluster of wires. 

A city has lots of roads, and a different name for each road.  A wire diagram designates a different color for different wires related to their function.

What you are doing now is following the roadway back to the battery POS terminal.  The wire color changes only when passing through an interchange or device, such as a switch.

Power on Red comes from the battery POS to the Key switch.  Key switch routes to the black wire distribution system.  All the black wires have the same purpose.  One of them goes to the stop-run-stop switch.  It passes power onto the Black/white which feed the coils.  The coil is simply a coil of wound up wire, so voltage in the black/white wire will appear on the Blue or Yellow when the point contacts are open.  The blue an yellow wires should only read Zero volts when the key switch or stop-run-stop switch prevent routing power, OR when the point contacts are closed.

If you have given up learning to read a wire diagram, then you'd better get the bike to someone who can.

Cheers,

[shade]

Is it a bad idea for me to remove the electrical tape wrapped around the large cluster of wires running up the frame?  It seems like the only way to try to trace the wires, but I don't want to do anything harmful.  Am I looking for something that has become disconnected or a faulty device of some kind?

[TwoTired]

There is seldom any need to unwrap the wire harness.  It is only necessary if physical damage is obvious, or a wire where it enter and leaves the bundle can be proven to carry different potentials (voltage).

You don't have to split a water pipe to follow the water, if it flows in one end and comes out the other, the pipe is working.  That's all a wire does; conduct electricity for one end to the other.

Do you have a problem identifying wire colors?

Am I looking for something that has become disconnected or a faulty device of some kind?

That is precisely what the voltmeter is for.  To follow an intended path of electron flow and find where the bridge is out.
Could be a connector, could be a switch, could be a device, could be a broken wire.  In each case, voltage will be present on one side of it and not on the other side of a faulty component.

Is it a bad idea for me to remove the electrical tape wrapped around the large cluster of wires running up the frame?  It seems like the only way to try to trace the wires, but I don't want to do anything harmful. 

I don't think that is going to help you.  You'll just wind up with a big confusing rat's nest that you will have to put back together later.

If you have given up learning to read and follow a wire diagram, then you'd better get the bike to someone who can.

Cheers,

[shade]

On the wiring diagram, it seems like the yellow and blue wires seem to just go from the points to the ignition coils?

In the picture below I checked the reading was 10.06 inside the open end of the yellow wire, and similar reading for the blue. 

[TwoTired]

Then your coils are getting power.

Now you need to find out why the yellow and blue don't route that power to the points when the contacts are open.

[shade]

Then your coils are getting power.

Now you need to find out why the yellow and blue don't route that power to the points when the contacts are open.

TwoTired, thanks for your help.  I know it is frustrating trying to explain this to someone who has no mechanical experience.  If you have any suggestions I would love to hear them.  There doesn't seem to be anything between the coils and the points, so what would I be looking for?  Could it be the condensers?  I'm wondering why it did get spark when I started but isn't now.

Also the starter button completely fell apart.  I am turning it over by applying a screwdriver to the contact in there now.  I doubt this has anything to do with it, but just mentioning it. 

[TwoTired]

If you are saying you found voltage on both the yellow and blue wires at the coil, but not at the place where they mount on the points, then disconnect the wires at the points and check it again.  If you don't get voltage on yellow and blue there then the problem is between the two connectors of the yellow and blue wires.  If you suspect the condensers, then temporarily disconnect just the condensers, and check for Y&B voltage again.  Remember that when the points close the voltage is grounded and you can expect to see none.  Only when the points are open can voltage from the coils be seen on the points terminals.

You should also make certain that the mounting posts on the points are insulated from any connection to the points plate.  That would bypass any points functionality and prevent the coil discharge which makes spark.

Save the starter button issue for the next item to repair.  For now, focus on getting spark.  There is always kick start.  And engine running will be a morale boost.

[Spanner 1]

Blue and Yellow wires are connected straight to ground at the points = no voltage readable at the connection , points open or closed  .... Wires probably connected behind the insulator, i.e. between the insulator and the metal point bracket..... look at a close-up pic. of the points to see correct insulator/wire combination.... has to be that OR the blue and yellow are disconnected at the side of the oil tank....... follow the wires out of the points cover under the motor and up to this connector , you'll see it... bet it's the first option tho'..

[shade]

I will examine the connections at the points as soon as it stops raining.
And just so you guys don't think I am going at this alone here is an image of my faithful helper (napping on the tarp.)

[shade]

I had the wires connected improperly to the points (thanks Spanner1.)  Connected them properly, stuck my screwdriver into the starter switch and...

IT STARTED

I know I have a lot of work to do on this bike but this is a major step forward, and it just feels great.  This forum and it's members are an amazing tool and a great group of people.  Thank you very much for your help.

I am going to smile for about a half hour before I start looking into what it's going to take to get this bike on the street. 

Thanks!

[Spanner 1]

Yes I, Spanner, am a tool... hehe    .... Glad it started