No spark after rebuild - problem solved!

[Madbuffalo]

It's been a long night of testing but we might have something. Here's what I tested, toward the end I found that the points that are not firing are not grounding properly when closed. The right point has good ground and is still firing.

Voltage at open point with V.R. disconnected and now with other points closed:
R = 12.3V, C = 10.6V, L = 10.7V

Voltage at points wires when disconnected from points and with V.R. disconnected:
R,C,L = 12.3V

Voltage through coils with point closed:
R = 9.9V, C = 0, L = 0

This didn't make sense to me. There is voltage at the point but not at the coil? Maybe the point isn't grounded. So I re-checked the resistance through each closed point, this time using the correct resistance setting on the meter:
R = 0.5ohms, C = 7.6ohms, L = 9.3ohms

Then I re-checked the voltage through coils, this time with wire clamps on the points that should be closed to ensure ground:
R,C,L = 9.1V

[Cliff]

R = 0.5ohms, C = 7.6ohms, L = 9.3ohms
With the points closed there should be NO resistance through them!! As simple as this system is, it relies on good, clean, no resistance contact to make it work! Make sure the contacts are clean and dry and recheck!!

[Madbuffalo]

Cliff,

R = 0.5ohms, C = 7.6ohms, L = 9.3ohms
With the points closed there should be NO resistance through them!!

Agreed. My meter has 0.4ohms of internal resistance so really the actual test numbers were: 0.1, 7.2, 8.9. I just went back out too and tried your idea to manually open the points to look for spark on the correct spark plug. I couldn't see spark on any plug even with all the garage lights out but it did confirm that there is only spark on the right point. I have tried additional engine/frame to battery grounds in various forms throughout the process. Thanks for the ideas.

[Cliff]

Ok. Let's eliminate the points and condensors. Again, with the key on, kill switch in run, remove the wire from one set of points and touch it to ground several times. Do you have spark at the plug? Do you have spark at the wire? Do the same with the other two sets. What happens?? Spark or not at the plug??? If you have spark, then all is good down to that point! The resistance through the points contacts could be the problem. Check for any dirt, corrosion or oil on the contacts.
Cliff!

[jabcb]

Coil resistance is ~ 4 ohm for all coils.
Voltage drop across coils with points closed: R 9.9V, C 0V, L 0V

From V = I * R
We get current with points closed: R ~ 2.5A, C ~ 0A, L ~ 0A

Resistance across closed points: R ~ .1 ohm, C ~ 7.2 ohm, L ~ 8.9 ohm

But the resistance across open C & L points is not infinite. With the points wired up, the circuit for open C & L points is:
1) wire from moving part of C or L point to coil
2) coil
3) orange wire from coil to orange wire on R coil
4) R coil
5) wire from R coil to R point
6) across closed R point
7) fixed part of R point to fixed part of C or L point
Resistance for this circuit would be around 4 + 4 + .1 = ~ 8.1 ohms (doesn't include resistance in wires)

Thats about what you got for closed C & L points.

What did you use to clean and dry the points?
Maybe the prior owner used something to clean the points that actually ended up hardening over the years to form a clear insulating layer.

Perhaps you should check the resistances for the other set of points that were originally on your bike.

Since you haven't done timing before, I suggest you discuss it on the forum before swapping out the points/plate.

[Madbuffalo]

jabcb,

What did you use to clean and dry the points?
Double sided 180 grit sand paper placed between closed point ends and dragged back and forth 5-6 times, then sprayed entire area with electrical parts cleaner, then paper towel on points. A couple days later I sanded again.

Maybe the prior owner used something to clean the points that actually ended up hardening over the years to form a clear insulating layer.
Could be. Also, the parts engine has likely been sitting for many years, although the points/plate looked brand new when I removed the points cover.

Perhaps you should check the resistances for the other set of points that were originally on your bike.
I did that. With original points/plate on workbench and all points closed I read 0.4ohms, or 0ohms actual.

Since you haven't done timing before, I suggest you discuss it on the forum before swapping out the points/plate.
As I mentioned Red has been very helpfull with the rebuild and I will call him to walk me through the process if I end up switching the points/plate. I would really like some sources for good dial indicators that can be threaded into the spark plug opening.

So it sounds like the points resistance is the likely culprit? In my opinion I've cleaned them as well as I can, unless you have a better method, so it may be time to do the points/plate switch?

Also noticed you've been helping someone else out with their 'no spark' issue. Sounds like you're our resident electrical guru. Thanks again for all the help!

[Madbuffalo]

We got it guys.

The resistance through the points contacts could be the problem. Check for any dirt, corrosion or oil on the contacts.

Tonight I took the left point OFF the bike (leaving the timing plate intact). At the work bench I was able to open it up and noticed thick black tarnishing on the point surface that the sand paper hadn't been able to remove. I cleaned it thoroughly with a file, put it back on the bike and tested 0 resistance when closed (was reading 8.9ohms). I spun the engine with the starter and saw strong spark on both the point and spark plug. This weekend I'll remove and clean the other two points and post what I hope is the final result.

[Madbuffalo]

Runs like a champ! I cleaned the other points, put them on and the bike started right up. It was the first time I've heard the bike really running since the engine rebuild so it's been a great night. Tomorrow morning I'll put the rest of the cosmetic parts on and it'll be finished. I want to give a huge thanks to everyone who posted ideas and suggestions, especially jabcb and Cliff. I couldn't have done it without you.

Josh

[oldjapanesebikes]

[Red Sloan]

[two-stroke-brit]

nothing like eventualy solving a vexing problem.
and being rewarded with that great sound.
well done.

[Cliff]

Runs like a champ! I cleaned the other points, put them on and the bike started right up. It was the first time I've heard the bike really running since the engine rebuild so it's been a great night. Tomorrow morning I'll put the rest of the cosmetic parts on and it'll be finished. I want to give a huge thanks to everyone who posted ideas and suggestions, especially jabcb and Cliff. I couldn't have done it without you.

Josh

Hey Josh!! Glad we could help! There's nothing sweeter than the sound of an engine firing up for the first time!!!
Cliff!!

[RING_DING]

Thanks to all the posts on this topic, I now have three fat sparks where I had none before. All I did was file and clean the points until I got zero resistance across all three.

[Madbuffalo]

Glad to hear my misfortune has helped someone. Personally I am sort of glad my whole ordeal with the spark happened. I learned a lot about my bike's electrical system where before I was afraid to touch anything electrical for fear of disturbing the mystical force that made it run. Again, glad you got it figured out.

Josh

[jabcb]

the mystical force explained...

"Any sufficiently advanced technology is indistinguishable from magic."
— Arthur C. Clarke