No spark advance for rear cyl - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 15 (permalink) Old 05-06-2019, 04:53 PM Thread Starter
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No spark advance for rear cyl

Hi, my "new" Vulcan 750 '98 has no ignition advance for rear cyl, front is ok. Any suggestion to solve this problem?. Top speed 70 mph.
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post #2 of 15 (permalink) Old 05-06-2019, 04:56 PM Thread Starter
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Has new pick up coils.
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post #3 of 15 (permalink) Old 05-06-2019, 06:24 PM
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The Vulcan has an engine advance?

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post #4 of 15 (permalink) Old 05-06-2019, 07:39 PM Thread Starter
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Yes, can test the ignition dinamic spark advance with a strobe lamp.Is totally controlled by the CDI unit.
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post #5 of 15 (permalink) Old 05-06-2019, 11:13 PM
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Don't really know, unless somehow the CDI isn't fully functional. Never had a timing light on mine. Some of us have been wondering about the start circuit wire running to the CDI, white/red or red/white, I've forgotten which.

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post #6 of 15 (permalink) Old 05-06-2019, 11:42 PM
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Hi Niko,
Among the regulars, nobody knows much about the specifics of the CDI box circuitry. It's been a mystery for some time.
Are there factory markings you are using with the strobe to check the timing? I'd be curious to see this on my own engine.
I know some people have used a file on the pickup coil mounts in order to change the ignition timing slightly, since modifying the CDI box isn't within the current knowledge pool.

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post #7 of 15 (permalink) Old 05-07-2019, 06:59 AM Thread Starter
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Red/White wire for the CDI unit comes from starter switch with + polarity. This signal to the CDI unit occurs only when the engine is in starting phase. I think that makes some kind of ease for starting the engine.
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post #8 of 15 (permalink) Old 05-07-2019, 07:16 AM
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Quote:
Originally Posted by Niko View Post
Red/White wire for the CDI unit comes from starter switch with + polarity. This signal to the CDI unit occurs only when the engine is in starting phase. I think that makes some kind of ease for starting the engine.
That's what some of us figured, but have never found out for sure what happens with it. I intended to check it out but didn't get to it. It should be fairly simple, watch with a timing light during starts with the red/white connected/disconnected.

On a cold start, some added timing advance can help, but on a hot start less advance is desirable for easy starts.

As far as I know, you're the first to check advance between the two cylinders. Was it running poorly? Edit: I see now, "top speed 70". I would look at fuel delivery, ... slide diaphragms, carb vents, float height, etc.

Using a strobe, independent of ignition signal, would not be accurate. The light needs to 'see' when the spark occurs. That's why a timing light uses the coil wire to trigger the light. With the strobe, you're only seeing the timing mark when the strobe flashes, but not when the actual spark event occurs.

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Last edited by Spockster; 05-07-2019 at 07:30 AM.
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post #9 of 15 (permalink) Old 05-07-2019, 07:47 AM Thread Starter
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With a timing light and the engine accelerating from 1000 to 4000 rpm, I can see that the top aluminum notch works smoothly from the blue to the green mark on the front cylinder. In the rear cyl I can see an erratic movement around the green mark.
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post #10 of 15 (permalink) Old 05-07-2019, 07:49 AM Thread Starter
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Excuse me, erratic around the BLUE mark.
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