Topic: 550K 78' Cylinders 2-3 not firing.

[radiowar]

Was riding home the other night and the engine began to behave to erratic. Felt like I lost a cylinder. Luckily I was 4 blocks from my house, so I was able to get home with out much hassle. The engine has 22K on it.

The next day I began to look for the problem. First thing I did was get the bike started. It was still rough, but I began to unplug spark plugs. I found that unplugging spark plug 2 and 3 made no difference.

OK great, one my ignition coils is gone. Or so I thought.

I began to measure resistance on the coils. I was measuring approx. 3.4 ohms on both coils (they are stock). I measured the secondary side, and found that I had an open circuit. cut the wires back a little bit to clean up the oxidation. Great I was measuring 28k ohms plug to plug.

Plugged everything back in started the engine, and no change. My next plan was to put the 2-3 caps on 1-4 and vise-versa. Swap the leads on the primary, and test again.

Progress. The problem swapped to 1-4. So I could unplugged 1 and 4 and there would be no change in engine performance.

Looked at the points, they were looking pretty good, checked them to make sure they were making good contact. Checked the static timing, and checked the point gap. All were good. These are a fresh pair of points and condensers with only about 300 miles on them.

Im at the end of my troubleshooting skills. Any thoughts from the Pros?

[seanbarney41]

try swapping condensors.  I have had new ones go bad before, especially if they are Daiichi brand.  Condensors are also difficult to test short of just swapping in a known good one.

[Deltarider]

Do you get spark without caps? Test with cable ends close to the engine.
If you suspect a condensor you may have a look at the video and see what difference a good and a bad condensor results in.

Here, the left condensor (1+4) is bad and the right condensor (2+3) is good.

[radiowar]

Ill take a look at the condensors, I suspect its a good place to start looking again.

I'm also going to make sure that the points have a good ground, I suspect I might be looking at a overall re-grounding of the bike.

[Deltarider]

I'm also going to make sure that the points have a good ground, I suspect I might be looking at a overall re-grounding of the bike.

I find points without a good ground hard to imagine. They can have a ground that is 'too good' however. 

[radiowar]

Problem Solved. It was the condenser on 2-3 all along, Next time in order some parts, i'm ordering spares.

[seanbarney41]

now I am curious what brand of condensor you were using...were they Daiichi?

[radiowar]

now I am curious what brand of condensor you were using...were they Daiichi?

Yes I had bought new Daiichi points and condenser's about 300 miles ago. I put the old condensers back on, and everything was back running.

[seanbarney41]

now I am curious what brand of condensor you were using...were they Daiichi?

Yes I had bought new Daiichi points and condenser's about 300 miles ago. I put the old condensers back on, and everything was back running.

I have had brand new Daiichi condensors fail in almost the same amount of miles.  Both condensors failed within 80 miles of each other....went kinda like this..."that's odd, my brand new 1/4 condensor has failed. (puts 35 year old oem one back on) must have been a fluke   (80 miles later)  WTF, now 2/3 has failed, this is no fluke!"  I will no longer use Daiichi parts.
      Even though I had long understood that Daiichi was crap quality, I continued to use them, as a local shop had them in stock for cheap...but its no longer worthwhile to use them.  Be careful, as most online sellers sell them without listing  what brand they are providing.  You are pretty much restricted to a Honda dealership or ebay.  Nippon Denso or Hitachi are what you want.

[Vinhead1957]

 The weak spot is how the yellow wire is connected. The insulator can grounded too easily. If the points are open there should be no continuity to the baseplate. The points provide ground when closed, firing the coil.

[Deltarider]

... firing the coil.

I suggest feeding the coil. For a good understanding, the coil fires when the points open.