66 cb77 right side spark issue

[Dlans]

The bike kicks over right away and stays running, however the right side is not firing, unless I pull the cap slightly off or take it off completely and let the wire spark to the plug directly. Why would it run with the cap partially off and not all the way pushed on?

 

[66Sprint]

Check a few things for us....

Resistance of plug cap.....

Gap of right points.....

Is that sparkplug a resistor plug? (what's its letter-number code?)

Right Coil secondary resistance?....

Plug gap?.....

Resting battery voltage?....

Is timing EXACT?

 

[ancientdad]

Moved to 305 Electrical and Ignition section.

And, it could simply be a partly fouled plug. Sometimes increasing the resistance makes a weak (nearly fouled) plug fire. My Dad taught me the trick of using a piece of thin cardboard (back when he learned it, a matchbook cover) wrapped around the upper part of the plug inside the plug cap (prehistoric caps and wires on his 1948 Harley) holding the cap slightly away from the tip of the plug so the spark had to jump twice, which would allow an oil-fouled plug to fire until it got a lot worse [on the rear cylinder of the bike he went off into a river with after getting run off the road].

 

[66Sprint]

I think the scientific answer will be a good addition to 66Sprint's Classroom......Give me some time to type it up......

 

[ancientdad]

I'll pass on the stories, you handle the science. :dizzy::dizzy:

 

[Dlans]

Resistance of plug cap.....
Right cap 8.68
Left cap 7.00

Gap of right points..... .30

Is that sparkplug a resistor plug? (what's its letter-number code?) D8HA

Right Coil secondary resistance?....
17.8

Plug gap?..... .025

Resting battery voltage?.... 12.63

Is timing EXACT? Yes to the best of my ability

 

[66Sprint]

Resistance of plug cap.....
Right cap 8.68
Left cap 7.00

Gap of right points..... .30

Is that sparkplug a resistor plug? (what's its letter-number code?) D8HA

Right Coil secondary resistance?....
17.8

Plug gap?..... .025

Resting battery voltage?.... 12.63

Is timing EXACT? Yes to the best of my ability

Let me guess...Auto-ranging meter......
IIRC, Plug caps should be 5000 Ohms (5K Ohms), and coil secondary ~18,000 (18K) Ohms.....
Since you are reading plug gap in inches, I'm ASSUMING you are using the same standard for points gap......Should be .012" to.016".......
IF your points gap reading was metric, 0.30 mm is acceptable....

When you remeasured plug gap, was plug carbon fouled or fuel/oil fouled?....IF either, try D7HA plugs.....

You may phone me at number below.....