Topic: Weird electrical problem, CB550, no power to one condenser [SOLVED]

[Kframe]

Today I was working on getting the '74 CB550K in tune, having just received a dwell meter and a timing strobe gun from my wife for my birthday.

Was getting things dialed in, was running smoother and sounding better, but all of a sudden cylinders 1&4 stopped firing entirely.  Cyl.s 2&3 were running enough to keep the engine going, but nothing at all from 1&4. 

So, tried troubleshooting a bit.  I figured if one condenser went bad that I could swap them and the problem would switch to 2&3, but no, the bike ran but still only on 2&3.  Visible spark in points gap on 2&3, no spark on 1&4 points gap. 

I traced the yellow and blue wires that go to the condensers back up the harness to where they connected to a larger harness near the battery, everything was connected.  So, then I switched the blue and the yellow at that connection to see if the problem would switch cylinder pairs, but no, this time the bike wouldn't start at all.
Reconnected everything to original. 
Checked voltage, with the engine running, at the points connection where the blue and green (from condenser) meet at the terminal, and likewise where the yellow and green meet at the terminal on the other points.  On the set on the right, which is for 2&3 I was picking up a voltage of around 6.something volts.  On the 1&4 side, only 0.72 volts. 
Then I tried to see if I could run a jumper from one terminal to the other so that they'd share the ~6 volts and the bike immediately died. 
Unhooking the jumper, the bike would again start and run on only 2&3. 

My assumptions: 
Both condensers are still good.
I should be getting more than 0.72v from the blue wire. 
I think that the ~6v from the yellow is okay (in spec) as cyl.s 2&3 run strong and accelerate well.

Both points are gapped at about .14", per brass feeler gauge. 

My questions, well, first does anybody know right away what's wrong?
Two, where do the yellow and blue wires come from? 

I'm assuming they feed the condensers which feed the points which sparks to trigger the ignition coils to fire, right?
Can I assume right now that my 1&4 ignition coil didn't blow?

Could I have inadvertently (and unnoticed) done something while moving the points plate around that could've shorted something out. 
Oh, and the points plate is back where I started, I marked them with a Sharpie for reference.
The main fuse is good, I heard no pop or spark at anytime, and I did my adjusting with the key off. 

Right now I'm confounded, so any pointers will be happily received.
Thanks!
 
-Kris

[Kframe]

I should also mention that by the time this problem cropped up the electric start wouldn't go any longer, the battery was getting depleted and I could kick it started every time (except as mentioning in the first post). 
So, I don't know if the voltages I reported were low or correct. 
Gonna keep the bike on the tender overnight and get back at it in the morning, hopefully with some direction.

[Kframe]

Been thinking about this and reading more in the archives.
Looks like I'm supposed to be seeing close to 12 (10.6-11.7 has been reported in other posts) so my 0.72v on the blue wire and 6ish on the yellow is not cool.

I also did catch a whiff of an electronicky ozone smell at one point this afternoon, is it possible that I fried the primary winding on the 1&4 coil? 

The other possibility is that I messed up the order of the spacers on the points terminal where the blue and green wires attach to the point assy, and maybe I'm making a direct short to the points plate (ground).  I'll check that first thing, hopefully this issue is as simple as that.....

I am pretty concerned that I fried a coil, looks like they're $100-150/pair. 

So first thing I need to check the wiring, then on to testing the coil (resistance/continuity checks) and go from there. 

I enjoy wrenching but electrical gremlins can be frustrating.

[TwoTired]

It might help if you refer to the wire diagram.  The Yellow and Blue wires connect between the point connections and the left or right coil.

The point terminals get whatever voltage is present from the coils, and closed points will make the point terminals "see" 0 volts, as they should make a firm connection to engine case or electrical "ground".

Closed points also make the current flow through the coils and this cause a voltage drop through them due to their resistance.

While running, the point terminals are going to see intermittent voltages, and your meter better be robust enough to withstand 300-400 volt pulses as back EMF from the discharging coils.

As to your sudden run issue, make sure the the post connections at the point are well insulated from the point set frame.  Unfortunately, the measurements you have taken so far, aren't enough info to make a positive determination.

Coils are pretty robust.  I don't think their is any way to connect them to a 12V power source and hurt them, short of also putting them in an oven during such an event.

[Kframe]

TT, thank you for the reply.
Yours was one I'd been hoping to see.

I'll check things over thoroughly tomorrow and report back.

[Vinhead1957]

I think it is a black/white wire that comes off the kill switch that goes to the coils.   Check that connection in the headlight bucket and at the coil for 12 volts

[CapeCafe]

I was having a similar problem when I did the 3000k tune on my 76 550k.  I installed the new points and condensors then set the gap.  When I checked for spark I didn't have anything on 1-4.  After trouble shooting through the coils I discovered I was not getting voltage through the 1-4 when points opened.  It turns out I had the clip for the new condenser on the 1-4 side touching the points plate and shorting it out.  I re-installed the clip and slightly bent it up to insure it didn't touch and it fired across all cylinders.  Easy thing to check for

[lucky]

Today I was working on getting the '74 CB550K in tune, having just received a dwell meter and a timing strobe gun from my wife for my birthday.

Was getting things dialed in, was running smoother and sounding better, but all of a sudden cylinders 1&4 stopped firing entirely.  Cyl.s 2&3 were running enough to keep the engine going, but nothing at all from 1&4. 

So, tried troubleshooting a bit.  I figured if one condenser went bad that I could swap them and the problem would switch to 2&3, but no, the bike ran but still only on 2&3.  Visible spark in points gap on 2&3, no spark on 1&4 points gap. 

I traced the yellow and blue wires that go to the condensers back up the harness to where they connected to a larger harness near the battery, everything was connected.  So, then I switched the blue and the yellow at that connection to see if the problem would switch cylinder pairs, but no, this time the bike wouldn't start at all.
Reconnected everything to original. 
Checked voltage, with the engine running, at the points connection where the blue and green (from condenser) meet at the terminal, and likewise where the yellow and green meet at the terminal on the other points.  On the set on the right, which is for 2&3 I was picking up a voltage of around 6.something volts.  On the 1&4 side, only 0.72 volts. 
Then I tried to see if I could run a jumper from one terminal to the other so that they'd share the ~6 volts and the bike immediately died. 
Unhooking the jumper, the bike would again start and run on only 2&3. 

My assumptions: 
Both condensers are still good.
I should be getting more than 0.72v from the blue wire. 
I think that the ~6v from the yellow is okay (in spec) as cyl.s 2&3 run strong and accelerate well.

Both points are gapped at about .14", per brass feeler gauge. 

My questions, well, first does anybody know right away what's wrong?
Two, where do the yellow and blue wires come from? 

I'm assuming they feed the condensers which feed the points which sparks to trigger the ignition coils to fire, right?
Can I assume right now that my 1&4 ignition coil didn't blow?

Could I have inadvertently (and unnoticed) done something while moving the points plate around that could've shorted something out. 
Oh, and the points plate is back where I started, I marked them with a Sharpie for reference.
The main fuse is good, I heard no pop or spark at anytime, and I did my adjusting with the key off. 

Right now I'm confounded, so any pointers will be happily received.
Thanks!
 
-Kris

The job of points is NOT to make a spark. IT is not a spark plug!
The points may make a small spark but that is not their purpose.

[CapeCafe]

I would first check to make sure you have continuity through your 1-4 coil.  Touch one lead of your meter to the blk/wht (power) wire and the other to the blue or yellow wire out of the coil.  Got continuity - check.  Next I would remove your points cover, make sure your on/off switch is ON, turn ignition switch to first position and use a socket to slowly turn your crank until you see the 1-4 points open.  Once open put the positive lead from your meter to the clip where the points and condenser are connected on the 1-4 side and the other lead to a good ground source.  You should see 12 volts there.  Then turn the crank again until the 2-3 side opens and check them the the same way.  Again, you should have the same 12 volt reading.

This is where I discovered my problem.  My 2-3 side had 12 volts and when I opened the 1-4 side and tested for voltage I would blow the main (15amp) fuse. I reinstalled the condenser clip on the 1-4 side, bent it up off the plate and low and behold she was a sparking at the 1-4 plugs. I made a completely new wiring harness, so I had the benefit of knowing all my connectors were solid and correctly matched.

[Kframe]

Got 'er fixed!  Turns out the problem was much simpler than I feared.
After I took the tank completely off in order to volt test a few different things, including the terminals at the coil, I realized that the blue wire bullet connectors had been pulled apart right near the coil.  Apparently there was still partial contact since I was picking up 1volt on the blue wire down at the points, but not enough to transfer any substantial current. 

Cleaned and reconnected the blue wire and rerouted it slightly to take tension off of it, and the bike ran on all four.

Rechecked the point gap and dwell (0.18ish) and 22.5 on the dwell scale (I'm using one with a scale for cars) and went out for a ride.  Idles much smoother now, pulls hard all the way up, and I went 40 miles with not one hiccup.  I think my mix is a bit off still as I only got 38mpg over that 40 miles (I filled up before and after) but at least I feel that I can ride the bike out on the road without fear of getting stranded miles and miles from home. 

Thanks for helping with the troubleshooting; yet another lesson reinforced - ALWAYS check ALL connections before troubleshooting further or worrying that components have fried.