--- Jim Muller <jimmuller@pop.mail.rcn.net> wrote:
> Randall's point, I believe, is that irregularly
> timed electrical
> pulses can cause an electic tach to misbehave.
> Floating points or
> badly out of spec dwell could cause this, as could
> loose wiring or
> ground behind the dash. However a mechanical tach
> isn't susceptible
> to this. A sticking cable might make the tach jump
> in much the same
> way that a speedometer can bounce. But the dwell
> angle (point gap)
> won't have anything to do with it, and worn dizzy
> shaft bushings
> probably won't either unless maybe possibly perhaps
> they cause a
> really bad gear fit. It's hard to imagine a
> mechanical tach hitting
> 12,000 for any other reason, unless your clutch
> slipped and the
> engine really took off, in which case I'd wonder
> that something
> didn't break.
>
Yeah, I wonder what the heck happened, too. The engine
speed did not change. The clutch didn't slip. I think
maybe the tach was complaining about the cold. The
needle went almost all the way around back to 0. I
guess I'll take the lawnmower and bicycles out of the
garage again this weekend and do some diags.
Cameron
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