Topic: Electrical Nightmare

[jwurbel]

Have a 72 750.  All points, condensers, wiring harness, and coils new within last year.  All Honda or Tec.  Coils were purchased 30 years ago but never mounted until last year.  I can’t get 2-3 cylinders to run.  Have tested plug caps, wires, condensers, and coils with multimeter .  All within specs.  Wire connection's are tight. Trouble light lit at coil connections, points and points to coil wire connections.  Grounded plugs against the block and have a good bright spark.  Took carb jets and cleaned them again thinking I might have a blockage.  But when I hit the starter, only 1-4 run.  At a loss.

Any ideas would be appreciated.

[BenelliSEI]

Assuming you have a healthy spark on 2-3 it must fuel. Does it run on 1-4? Squirt some starting fluid down 2-3 carbs and see if it fires. Then you know it’s carbs for sure.

[jwurbel]

Runs on 1-4

Will consider starter fluid as an option

[jwurbel]

Just an addendum to my answer.  It just seems unusual that the problem is with 2-3 which are definitely part of one firing set.

[Deltarider]

What do the 2+3 plugs show after an attempt?
Wet and smelling of gas? Check the ignition once more.
1. Clean the points surfaces (once more) with a little alcohol or aceton. I've learned that even after having had a piece of plastic card or paper between the points, I had to clean them.
2. Make sure spark is not lost between HT leads/plugcaps and the head.

[newday777]

Just an addendum to my answer.  It just seems unusual that the problem is with 2-3 which are definitely part of one firing set.

Replace the 2-3 condenser with an old TEC condenser.
I had a friend's K4 750 on the lift that I struggled with like yours until I put on an old whole points plate assembly I had in my drawer.
The 2-3 condenser on his plate failed while I had it on the lift between the time I had put on the new replacement coils, caps and new plugs. Had me scratching my head and pulling my hair out for a couple nights until I did that, then it fired off real good. It's still running great 6 months later.

[jwurbel]

Update:  Retightened everything again and found one point set of wires loose. Retested condensers with older Tec unit and everything working.  However, when fired up 2-3 still seems to be missing.  Pipes warmup but nothing hot like 1-4.  Idling up and down as if the coil is shorting out.  Turned off and took a trouble light to the 2-3 points. Light lit and engine turned over to my surprise.  Checked plugs and they are not gas fouled.  So I am back to still searching for an answer.

[69cb750]

Update:  Retightened everything again and found one point set of wires loose. Retested condensers with older Tec unit and everything working.  However, when fired up 2-3 still seems to be missing.  Pipes warmup but nothing hot like 1-4.  Idling up and down as if the coil is shorting out.  Turned off and took a trouble light to the 2-3 points. Light lit and engine turned over to my surprise.  Checked plugs and they are not gas fouled.  So I am back to still searching for an answer.

This is like Vegas ...
My guess is coil or condenser cause thats what it usually is.

[newday777]

Update:  Retightened everything again and found one point set of wires loose. Retested condensers with older Tec unit and everything working.  However, when fired up 2-3 still seems to be missing.  Pipes warmup but nothing hot like 1-4.  Idling up and down as if the coil is shorting out.  Turned off and took a trouble light to the 2-3 points. Light lit and engine turned over to my surprise.  Checked plugs and they are not gas fouled.  So I am back to still searching for an answer.

Are you saying that you put in another condenser or what??

[Kevin D]

Are the fiber washers in order?
With the conductors away from the point frame?

[jwurbel]

I did and I still have the problem.  One additional thing I noticed was this.  If I tried to start it more than 2-3 times, the starter struggled as if the battery had drained.  Yet when I tested the battery, it showed 12.7 volts.

[BenelliSEI]

Those are th classic signs of a dead battery. Leave the voltage tester hooked up when you crank. If the battery is done, you will see the voltage plummet as you engage the starter…….

[MauiK3]

+1 on fiber washers, easy to miss this item.

[jwurbel]

Fiber washers repositioned.  And the battery is on the way out.

Will starting later..

[jwurbel]

Find out, due to testing coils and remounting, that I put the bracket on backwards. As such, bl/wt wires were grounded and consequently blowing fuses. Refit and that issue gone. However now no power at points.  When testing yellow and blue at the coils with ignition on, trouble light on.  When connected to blue/yellow to points, light goes out at the coil wires.  So I still am hunting.

[Don R]

 Follow the black/white wire, it gets power from black when the key switch is on, that goes into the red kill switch (on/off/on) on the right control, comes out black/white and goes to feed the coils. The blue and the yellow go from the coils and make ground through the points at the condenser to complete the circuit. Blue and yellow may show power depending on whether the points are closed or open.
 

[Deltarider]

[...] However now no power at points.  When testing yellow and blue at the coils with ignition on, trouble light on.  When connected to blue/yellow to points, light goes out at the coil wires.  So I still am hunting.

Frankly, I don't understand what you mean nor how you test.
With the IGN ON you should read around 10V between the points when open, when closed zero.
You could also check for continuity. You need an Ohmmeter for this and the IGN should now be OFF. I'd isolate the breakerpoints with a piece of plastic as shown in pic. One probe to a coil NEG and the other to the tiny bolt on the corresponding breakerpoints. When there is continuity, which is good, the meter will read near zero. If the meter doesn't do that, there is no continuity and you will have to check the wire.