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 Tach/dwell Repair or Adjustment 
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Joined: Sun Jun 23, 2013 1:41 pm
Posts: 366
Location: Phila. Penn.
In the process of troubleshooting a recurring miss on my wagoneer, I checked the carb for dirt and then was resetting the idle mix. However the tach/dwell meter was showing lower rpm than how the engine sounded (around 500 rpm). Fine. I have another still in its package someone gave me. Hook the 'new' one up and reads nearly 300 rpm higher. Nah, that ain't right either.
So, I hook up my digital timing light, and it shows an rpm that seems right (about 640 rpm).

Can I assume the tach in the digital timing light (innova dialback) is relatively accurate?
Is there a way to adjust or repair an analog tach/dwell meter that is so far off?
- What can go wrong with these?

Ignition is a Duraspark breakerless. RPM/Dwell is measured off the coil's negative.


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Thu Jan 21, 2016 10:50 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1704
I would double-check them on other engines before deciding the meter is at fault. A bad plug wire will cause erratic fly-back voltage spikes which can confuse the meter.


Sat Jan 23, 2016 2:26 pm
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