Quote:
Originally Posted by Alex
Sam - the issue is that people's tachs are already variable; it's not a very precise instrument. Exactly 50 mph will not be exactly 6000 rpm on everyone else's tach. On some it will show 6500, some it will show 5500, and neither one of those necessarily has the CDI issue. In addition to tach & speedo display variability, the rolling circumference of the rear tire matters as well, so anyone with either a brand new tire or worn tire, or even a completely different sized tire will show a difference of engine rpm --> speed conversion, with or without the CDI issue.
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I don't think tachs are as variable as you indicate - most are made to a spec which does have a + or - tolerance, but I have yet to see tachs that read way different from each other as in your example. You might get a slight variance of 1-200 RPMs (which is pretty hard to discern on the tiny 250 tach anyway), but not 1,000 RPMs as you indicate among bikes/vehicles of the same make/model/year.
That was why I tried to stay away from spelling out a certain RPM at a certain speed for everyone to compare against (no way to account for all the variables on individual bikes). Everyone should be able to tell on their bike though, whether the RPMs are displayed different at the same speed in the same gear with the bike COLD vs. WARM.