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Best way to test CDI and coils on 1981 750 LTD 4 cylinder
- Strickland
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- 1981 750 LTD
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15 May 2021 14:49 #848500
by Strickland
Best way to test CDI and coils on 1981 750 LTD 4 cylinder was created by Strickland
I have a 1981 750 LTD that I bought new in 81 and love it! Recently it started to have missing problems. I found a used CDI online and put it on. All the problems went away but my son left it out in the rain one night and the problem came back How can I check the system to figure out where the problem is? I know which cylinder is having the problem but not sure where to go. The coils were replaced about 3 years ago with Dyna coils. Thanks for your support!
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- Nessism
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15 May 2021 18:07 #848506
by Nessism
Replied by Nessism on topic Best way to test CDI and coils on 1981 750 LTD 4 cylinder
First off, your bike doesn't have a CDI. It has a transistorized ignitor box which functions on a different principle compared to a CDI. Anyway, if rain caused a problem I'd remove the electrical connector on the ignitor and spray some contact cleaner on them to make sure everything is clean. Do same on the coil and lead for the cylinder that isn't firing. That's where I'd start anyway.
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- TexasKZ
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16 May 2021 13:27 #848549
by TexasKZ
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
Replied by TexasKZ on topic Best way to test CDI and coils on 1981 750 LTD 4 cylinder
Could also be water pooling around a spark plug. A quick shot of air and some contact cleaner (not WD40) should do the trick.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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- Mikaw
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16 May 2021 13:57 #848552
by Mikaw
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
Replied by Mikaw on topic Best way to test CDI and coils on 1981 750 LTD 4 cylinder
Why not WD40?. I thought you only needed two tools. Duck tape and WD40.Could also be water pooling around a spark plug. A quick shot of air and some contact cleaner (not WD40) should do the trick.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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- F64
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- 81-KZ440D2
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16 May 2021 15:14 #848555
by F64
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY
Replied by F64 on topic Best way to test CDI and coils on 1981 750 LTD 4 cylinder
It's weird that it's affecting just 1 cylinder. A bad igniter circuit would affect cylinders in pairs as would a bad coil.
My guess is a bad spark plug or mixture issue that affects that one cylinder.
Swap the spark plugs and see if the problem stays or moves cylinders.
Swap spark plug wires on the coil with the misfiring cylinder to eliminate the wires. One of the wires could be arcing to ground.
Fire up the bike at night. Turn out the lights and take a water bottle and mist water around the coils and spark plug wires. If you have an arcing problem, the spark will be evident.
My guess is a bad spark plug or mixture issue that affects that one cylinder.
Swap the spark plugs and see if the problem stays or moves cylinders.
Swap spark plug wires on the coil with the misfiring cylinder to eliminate the wires. One of the wires could be arcing to ground.
Fire up the bike at night. Turn out the lights and take a water bottle and mist water around the coils and spark plug wires. If you have an arcing problem, the spark will be evident.
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY
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- TexasKZ
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17 May 2021 14:56 - 17 May 2021 14:57 #848625
by TexasKZ
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
Replied by TexasKZ on topic Best way to test CDI and coils on 1981 750 LTD 4 cylinder
Your toolbox is missing the essential tool, known as a Harley tool or BFH.
Why not WD40?. I thought you only needed two tools. Duck tape and WD40.Could also be water pooling around a spark plug. A quick shot of air and some contact cleaner (not WD40) should do the trick.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
Last edit: 17 May 2021 14:57 by TexasKZ.
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