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Tach accuracy

Old 07-28-2015, 07:35 AM
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Tach accuracy

Finished valve adjustment, the sync'ed carbs (Twinmax), then set pilots per manual drop test. Which is an enormous PITA (for me). Ended up just running the screws out to a set amount. Going to ride and tweek form there.
To set RPM I used an old, but in new condition a Sears engine analyzer I have owned since new from the '70s. It's an inductive pick-up for RPM, has a high and low RPM range, 0-1200 and 0-~6000. seems to be very sensitive and smooth in operation. Though a bit slow to react, Of course it's analog. Big face, needle has about 6 inches of arc where the RPM scale is. I'm getting the same repeatable readings on both high and low scales.
I'm getting about 500 RPM difference between the bike's tach and the tool.
The bike is reading higher. It sounds a little fast at idle for what ever that means.
Which do you think is right? My thinking is to adjust to what feels right and say good enough.
I'm procrastinating. I don't want to do a material run 60mi. round trio the the big orange box.
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Old 07-28-2015, 01:58 PM
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If you still have documentation on that tool it may say what the accuracy is... or you may be able to find a tool that states its accuracy and test against that
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Old 07-28-2015, 05:23 PM
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Don't have another tach to try, but just occurred to me to hook it to my truck for a comparison.
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