Lost tachometer and maybe a cylinder - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 18 (permalink) Old 07-25-2019, 06:41 AM Thread Starter
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I swapped another stator and r/r last night. The bike started up fine to morning but part way into my ride there was a slight jolt and the tachometer went to 0. I couldn't tell if the cylinder went as well since I was babying it until I got to work. I am confused since it felt fine for the first part of the ride. I am pretty sure I oriented the stator correctly. What could have gone wrong? The temp gauge and lights still work on the tach
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post #2 of 18 (permalink) Old 07-25-2019, 07:06 AM
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Possibly lost one of the coils, or there's a bad connection. The tach runs off one of the coils.

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post #3 of 18 (permalink) Old 07-25-2019, 07:26 AM Thread Starter
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Would that also explain the suspected cylinder loss of power? How can I test it?
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post #4 of 18 (permalink) Old 07-25-2019, 07:31 AM
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Yes, a dead coil means one cylinder won't get spark.

Just check for spark on each cylinder.

I could be mistaken and the tach runs off one of the pickup coils instead. I remember seeing it posted, but forget at this point if it's an ignition coil or pickup coil. Either one would kill the spark on one cylinder.
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Last edited by Spockster; 07-25-2019 at 07:34 AM.
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post #5 of 18 (permalink) Old 07-25-2019, 07:40 AM Thread Starter
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Thanks for your help. I'll check it when I get home. I'll know for sure by then if my cylinder isn't working anyway. Could something with the stator install have caused these issues if it's not a coil?
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post #6 of 18 (permalink) Old 07-25-2019, 07:43 AM
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Originally Posted by Chris Allunario View Post
Thanks for your help. I'll check it when I get home. I'll know for sure by then if my cylinder isn't working anyway
One cylinder running much cooler will show which one is dead.

Will need to crank the idle way up, by about 50%.

No, the stator shouldn't affect just one cylinder.

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post #7 of 18 (permalink) Old 07-25-2019, 07:58 AM Thread Starter
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It did idle when warmed up without adjusting the screw. It just seemed a bit off to me but that could be because I was panicking a bit about something for work combined with the tach not working
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post #8 of 18 (permalink) Old 07-25-2019, 03:43 PM
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So, according to the wiring schematic, ignition coil 1 (front?)'s primary coil's ground is tied to the tachometer.
That means that when working properly, the CDI box is providing a temporary path to ground each time a spark should trigger.

If the tach is dead, there's no path to ground, which means either a broken wire between the tach and the CDI box, the CDI box has failed, or the pickup coil that triggers the front cylinder has failed or has an open wire (black/yellow, black wire pair, lower pickup when looking under the engine cover).

I guess it's also possible that the primary coil in the ignition coil might have failed 'closed', somehow overpowering the pulsed signal, but that's unlikely.

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Last edited by Thorn; 07-25-2019 at 03:53 PM.
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post #9 of 18 (permalink) Old 07-25-2019, 06:54 PM
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check for bad connections under the left neck cover.. all the wiring for the handle bars and gauges have connections there.

while changing the stator itself will not effect ignition, a broken wire on the pickup coils could, and they are delicate. and you may have broken a wire while working on stator

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post #10 of 18 (permalink) Old 07-25-2019, 07:56 PM Thread Starter
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It's definitely the front cylinder that's the problem but the coil tested 2.4 ohms on the primary and open on the secondary (the rear coil performed the same on secondary). The manual says 2 ohms Max but it's not THAT far off. Are the coils the same? They're part numbers differ by a letter but I can't imagine them being different really since the timing should be handled elsewhere in my mind

Also the ground wire to the coil tested well to ground and I'm getting power at the red hot wire at the ignition coil

Last edited by Chris Allunario; 07-25-2019 at 08:04 PM.
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