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Symptoms for irregular tach input? 82 CM450e

Kentonius

Veteran Member
Joined
Jun 16, 2021
Total Posts
124
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0
Location
Inman, KS
I’ve put a couple different tachs on my 82 CM450e (for fun, you know), and each one has exhibited an irregular tach reading. It will hang, it will jump, but it will not be smooth up and down, or accurate for that matter.

I have it wired directly to the yellow wire before the coil.

What’s up? Any ideas?
 
I should also mention that the engine revs up and down just fine, smooth as butter.
 
LongDistanceRider said:
I would think it's the tach, the only thing other than that would be the connection to the Yellow wire.
Click to expand...

I don’t disagree. But I had a Trail Tech Vapor for a while, and now just your universal Amazon version. Both had the same tach input issues. I used a different wire, didn’t use the “T” connector for the second one and just spliced the wires together, etc. It’s odd. I also had my coil with the brown wire on the + and the red wire on the - when I looked at it, from the original owner.
 
That's an odd coil wire coloring, sounds like an aftermarket one that might not be correct. Check the primary resistance of the coil.
I've never had an issue with my TrailTech Vapor running the GM coil mod.
 
I probably should have been more specific. I have the yellow/green with plug on one end, but it was the other end of the coil that the red was on - and the brown was on +. Flipping them didn’t seem to make a difference.

Could it be the CDI? Not sure if that would even be possible since the engine is smooth and does not match the tach.
 
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