85VT700 Ignition Issues - Honda Shadow Forums : Shadow Motorcycle Forum
 
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post #1 of 8 (permalink) Old 04-23-2019, 08:48 AM Thread Starter
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Model: VT700
Year: 1985
Location: West Coast Florida
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Question 85VT700 Ignition Issues

Does anybody have a spec for testing the CDI modules for 85 VT700, or do I have to swap modules to figure out if one is bad? Are the CDI\s somewhat interchangeable across model years?



Background: Rebuilt carbs and engine to 0-time. Fixed issue with bad fuel pump relay and replaced fuel pump, so getting plenty of fuel. Engine starts and runs fair with some roughness; but hesitates initially when throttle jazzed. After engine warms up, starts running like crap, Only smooths out at about 4000 RPM, but likely because rotation is fast enough to mask the miss. Feels like hitting intermittently on one ore both cylinders.

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post #2 of 8 (permalink) Old 04-23-2019, 12:47 PM
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There are no tests in the manual unfortunately.
Swap side to side to see if it make any difference. Maybe a coil is breaking down also. Spray water on the coils and wires at idle and revved, to see if they arc over.
What color are the plugs? If too lean or too rich it may act like that.


Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #3 of 8 (permalink) Old 04-23-2019, 02:07 PM Thread Starter
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I'm liking the idea of checking the coils as well. The CDI units are on the rear fender away from the engine, but the coils are up front where they could easily be affected by engine heat. I also need to look at the part numbers on the CDIs to see if they are swappable. I'll keep you posted... THX
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post #4 of 8 (permalink) Old 04-23-2019, 02:15 PM
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The coils have been know to crack with age. Also measure the plug wire end caps should be about 5000 ohms resistance. And the coils can get corrosion where the wire screw in.

Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #5 of 8 (permalink) Old 04-23-2019, 06:32 PM
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You may well be right on the ignition being a problem, but I have one question based on your description.
Do you have the full air filter assembly hooked up, typically Honda Shadows run like crap without it?
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post #6 of 8 (permalink) Old 04-23-2019, 07:29 PM
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Actually that sounds like a carburation issue.
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post #7 of 8 (permalink) Old 04-23-2019, 07:29 PM
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That is a big 10-4 on the air intake tubing !

Only a biker knows why a dog sticks his head out of a car window.
1983 750 Shadow
From the past=
1951 Cushman scooter
1962 Honda 305 Dream
1965 Honda 305 Dream
1971 Honda 175 scrambler
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post #8 of 8 (permalink) Old 04-24-2019, 01:34 PM
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86 VT700C here... found a huge crack in one of my coils. Replaced. Runs alot smoother
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