Topic: CB125 No Spark...at a loss

[madScientist]

I've been working on getting a 74 125s running. It has good compression and I've rebuilt the carb...last was ignition which is where I'm stuck.

I had no spark at the plug and even after adjusting the points, had no spark. So I bought and installed a new point, condensor, and spark plug...still no spark so I'm working backward.

With the key on, I have voltage to the coil (black wire) and both the green and blue wires at the condensor. I unplug the green wire to the points and it has voltage. I plug it in but have no voltage to the breaker. I've readjusted the point at least 20 times. I do this by rotating the engine to where the cam lobe is at it's highest point on the slipper and set the point gap to .012. Rotating the engine with a test light on breaker band, I never see the light come on so I think i've isolated the problem to something with the points. What else can I check? What am I doing wrong?

Also, fwiw, I put a new battery in that is putting out about 6.4 volts. The rest of the electrical seems to still work although the turn signals are SUPER slow to blink but, from what I remember, that's how they've always been on this bike (had it for 20 years or so).

Any help is greatly appreciated...really want to hear this old thumper run.

[madScientist]

Bump? Is this not in the right area or am I doing / missing something really stupid?

[Kevin D]

Put up a picture of the points. Do you have the insulating washers and wires correctly? The point wire meets the condenser wire on top of the insulating washer. DAMHIK

[madScientist]

I believe they look right (to me).

I gapped it again and still have no spark. The point doesnt look like it ever makes contact though.

[jgger]

If the points don't ever close you will not get spark. It looks to me like it is wired correct.

Try adjusting the points down to where they close and still open. Don't worry about the gap right now,  then see if you're getting spark. Also if that bike has a kill switch,  make sure you don't have it set in the off position. Once you get spark then you can fine tune things.

Good luck

[scottly]

I believe they look right (to me).

I gapped it again and still have no spark. The point doesnt look like it ever makes contact though.

The terminal on the points wire may be grounding to the point plate on the back-side. Try rotating it so the wire is parallel with the plate.

[madScientist]

Excellent thanks guys! I'll try both and see where I get.

[Kevin D]

Move the spring to the outside of the mounting screw. Looks like the spring is touching the adjusting screw.

From cmsnl:

[madScientist]

Move the spring to the outside of the mounting screw. Looks like the spring is touching the adjusting screw.

From cmsnl:

That was it. I didnt notice I had the ground spring set wrong...probably should have since it made that inner screw a LOT easier to adjust when i had it the right orientation.

Flipped it around, reset the points, saw spark...started up on the first kick.

Thanks again!

[Kevin D]

Excellent!

I did the oil change on my CB today. It started right up after 5 months layup. Twice around the neighborhood, now I'm waiting for 55f or better.

OTOH, I was given an old Toro/B&S mower, it's not starting well. I have given it a once-over but it's not responding. Ether helps, so does sonny on the starter rope instead of me.

[madScientist]

I'm going to be waking my 750F up this weekend. That should be exciting! Spring is right around the corner!!