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Motorcycle Repair/1986 honda shadow 700

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Question
i have a 1986 honda shadow 700. the ignition coils power one to the front cylinder plugs and one to the rear cylinder plugs. when testing the spark i have spark on the front and rear on the right side but none on left side. since the coils are for front and rear cylinders i don't understand how i am not getting left side spark. if you could help it would be great.
Thank you,
Tim

Answer
Tim, it is pretty unlikely that both coils have failed, but it is worth checking the spark plug caps/wires for excessive resistance. They should be about 5k ohms. Double-ended coils have the unique feature of sparking from center electrode to the grounded tip on one plug and just the opposite on the other spark plug. Sometimes the spark isn't so apparent on that plug end when looking at it by eye.

Remove both plug caps/wire and check the coils for spark to ground with plain solid core wire. If you do actually have spark, look for air leaks in the carburetor manifolds and the air cut valve diaphragms that can mimic no spark running at idle.

You can also check the coils for matching resistance values on the primary and secondary wiring sides. If both coils match up, you probably have issues with the plug wire/caps instead. You may to change out the old hard to find wire leads with new separate spark plug caps and new wires.

Bill Silver

Motorcycle Repair

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Bill Silver

Expertise

Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.

Experience

I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

Organizations
VJMC (Vintage Japanese Motorcycle Club) of North America

Publications
VJMC newsletter, as editor for two years and as contributing editor currently.

Education/Credentials
3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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