[Shop-talk] Echo string trimmer

[David Scheidt]

On Fri, Jun 11, 2010 at 1:43 PM, Pat Horne <pat at hornesystemstx.com> wrote:
> A few days ago I was cleaning out a fence line. The string trimmer was doing
> fine. Then it was as if someone just turned off the switch, it slowed from
> full speed to stop without any poor running or noise.
>
> The fuel is fresh, with the correct mixture.
>
> I gave it a shot of ether to see if it would start, it did not respond. To
> me, this rules out a fuel problem.
>
> I replaced the plug, which looked good.
>
> After a trip to the local lawn equipment shop I was told that compression
> was low, and that I should just buy a new trimmer. They also said that I had
> a 4 cylinder spark plug in it, and that they run hotter than the 2 cycle
> plug, possibly burning the piston.
>
> I didn't think that the compression was any lower than it has been for
> years, so I brought it home and pulled the cylinder. The piston looks fine
> and the rings are not stuck. There is no scoring of the cylinder or piston.
>
> I connected a neon electrical test light from the high tension lead to
> ground and got a spark. Connecting the light in series with the plug and
> lead did not produce any light. I figured that the coil went bad. I have a
> spare engine from a Mantis tiller that is made by the same company as the
> Echo, so I mounted up the coil from that engine but got the same results.
>
> The shop said that in their 30 years of being in business they have never
> seen an ignition coil or flywheel on these engines go bad.
>
> My money is on the ignition. Anyone else have any guesses?

Do you have an inductive spark tester?  (A timing light will work, if
you hook it up to another 12v source) Is the HT lead part of the coil,
or a seperate part?  I'd bet on that.  But yeah, that smells like an
ignition failure.  I've seen the magnets break off the fly wheel.
There's also a capacitor in most magnetos.

I suspect the reason they've never seen one fail is because people say
"hum.  80 dollar tool.  100 dollar shop bill."

-- 
David Scheidt
dmscheidt at gmail.com