1976 CT power to the sparkplug boot but no spark from the actual plug

manowarkid

New Member
Hello all, i hope some of you may have an answer for me. I have a 1976 ct70, which ran well for about a half year before mysteriously dying on me mid ride. We replaced alot on it once that happened, new condensor, new points, new ignition coil, new sparkplug. Nothing. Everything was installed just as it was when we pulled it apart (how it was installed when the bike ran aswell).

Well today i went out and tried to get it going again, i tried a few things. I tested the new ignition coil (and the old one) and the numbers were as follows

New:
2.5 ohms
8.1k ohms

Old:
2.5 ohms
9.5k ohms
But the boot itself had no continuity (kicking myself if that was the original issue)

i tested with a test light to ensure i had spark going to the boot and i did, the light when off immediately when the bike was kicked (ground to engine block, testlight inside plug boot) however when i tried 3 different sparkplugs (all for ct70) they dont spark.

i also tested the stator windings with the testlight, and those worked too.

I suppose my questions are as follows:

1. The manuals say the ignition coil should measure atleast 9k ohms, mine is 8.1k, would this prevent the sparkplug from firing?

2. Would weak spark be my issue if i am getting power at the boot? What would be causing weak spark?

3. Would the condensor being bad allow a reading at the boot but no actual spark? How about bad timing, could it do that too? I figure bad timing would still get you spark, just at the wrong time.

Thank you for your time.
 

lukelaw1

Active Member
Can you get good spark with boot removed and high voltage lead held close to the head while kicking over? FYI have plug removed so the bike will turn over easier and faster. you may have a bad boot.

do you have a digital multi meter?

Ignition coil rarely fail.

weak spark could be "fouled" points, bad/weak condenser, bad coil on the stator plate.
If the points gap could cause weak or no spark, either to wide (not closing) or narrow (not opening) point should just start to open at the "F" mark to the case notch.

I believe a 76 has a bar control kill switch?
Check the bar switch and ignition switch. the switches simply ground the ignition.
One thing you can do is isolate the ignition circuit, hook the coil directly to the stator plate and see if spark is better.
pics would really help here.
 
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