Topic: (Solved) Everything was fine, then out of nowhere, no spark on #1 and #4

[NastyNip]

Here the rap (1978 CB550K Bone Stock):

Everything was great on the bike, and it was being ridden daily. I eventually noticed a little stumbling/flat spots so I decided to static check the points/timing and sure enough, they were a little out of spec. I loosened up the 1-4 points and adjusted the gap, tightened down and loosen and adjusted 2-3. I was checking the timing and noticed that all of a sudden, only 2/3 spark, and 1/4 don't.

I checked by grounding brand new plugs to the block and slowly rotating to F. Sure enough, only 2/3 produce spark and 1/4 do not. I have cleaned the points and re-adjusted twice, to no avail. I have searched previous threads and the common issues (blue wires grounding on the plate, points mis-adjusted) I don't think apply here.

When I arc the 1/4 point with a screwdriver, it sparks and also sparks the 1/4 plugs when grounded, but it does not produce a spark when rotating the crank, which led me to believe that the points weren't touching (is this hypothesis correct?), but I made sure they were touching and sure enough there is still no spark.

So what do I do now? I do not have alot of money to just go out and buy new parts, so hopefully there are some easy diagnostics/troubleshooting I can do before having to drop money on parts. Thanks guys.

[NastyNip]

Oh forgot to add: I have a pretty much new (less than 3k miles) TEC plate/points, and a fully charged battery.

[70CB750]

I asume that your SOHC fires 1+4 from one coil and 2+3 from the other coil just like 750.  If that's the case, switch coils - that will help eliminate the problem.

[NastyNip]

I asume that your SOHC fires 1+4 from one coil and 2+3 from the other coil just like 750.  If that's the case, switch coils - that will help eliminate the problem.

Correct, 1/4 is one coil and 2/3 is another. I'm going to run downstairs and check right now, by inversing the yellow/blue wires going to the points, correct?

However, if the 1/4 points spark when gapped by a screwdriver, wouldn't that mean the 1/4 coil is fine? (I'm learning as I go along)

[jamesbekman]

You could also just switch the spark plugs from 2-3 to go to 1-4 and see if the problem of no spark now is in 2-3 cyl.

[70CB750]

Just to verify spark all you need to do is what James says.  To make it run on the other two cylinders - if the culprit is indeed the coil - you will need to switch wires and cables.

Any more info since yesterday?

[NastyNip]

So I spent the night going through each connection and cleaning them nice and good. I switched the coils and the spark still didn't work on 1/4, and 2/3 were still firing. (which I assume means the coils are good, the problem lays somewhere around the points)

This led me to take a good hard look at the points, and after a beer or two I decided to take apart the 1/4 point (arm?). Believe it or not, but a REALLY REALLY REALLY small microscopic bump had formed on one of the point surfaces, creating what I assume to be bad contact between the points. Using fine sandpaper, I flattened it out as best I could, reinstalled, gapped and timed it.

BOOM, starts first try now, pulls hard.

I couldn't believe that such a small (seriously, probably smaller than the period at the end of this sentence) burr could affect such a beast as a SOHC.

Thank you for the help 70CB and James, with your help I was able to deduce the problem area and learn to pay attention to the fine details!

What would cause light pitting like that on such new points? Or is that just to be expected? No wonder everyone here hates points!

[Xnavylfr]

That pitting on the points is actually the points burn point. When the points spark they leave a small deposit/burn just like you would get if you just arced your welder to see if you have juice.


Xnavylfr(CHUCK)

[70CB750]

What he says ^^  - your little private EDM process 

That's why people revert to Hondaman ignition, it dramaticalluy decreases the current in points and they last long, long time.

Glad you were able to resolve the problem!