- Discussion on possible causes of and
solutions to a fouled spark-plug. Demonstrates governor spring tension
increase to raise operating speed.
The next thing you want to do is pull the
spark plug out of it so Iím just going to pull the wire off, push it
aside. Put a socket wrench on it nice and easy, spin it out and have a look.
- Itís quite clean, itís got some
blackness to it but thereís no large deposits. Looking at the insulator
around the electrode in the centre, thatís not cracked, thatís very
important. Inspect the insulator, hereís the insulator on the outside.
Thatís the electrode.
- This sparkplug is a little bit blackened, a
little bit fouled, you would say. Now the most likely cause of this is
overfuelling or a rich fuel condition. Reasons for a blackened or carbon
deposited spark plug would include things like too rich a fuel mixture or a
sticking choke or a clogged air cleaner, you know, anything thatís going
to increase the fuel in the fuel : air ratio. Also a good possibility is oil
seeping past the rings on the compression piston and getting up into the
combustion chamber and fouling it.
- I had the good sense to hold onto the
literature that came with the lawn mower when I bought it ten years ago. See
it says right here the gap on the spark plug should be thirty-thou so
weíll just check that with the feeler gauges. Itís pretty much a perfect
fit for thirty-thou so thereís nothing wrong with our gap. Clean it up
with a nice soft wire brush and reuse it.
- Anyway, so there is no adjustment here. The
only adjustment I can make is I can bend this metal tang, right here that
the governor spring is controlled by and that will speed up my high end.
This is the governor spring right here and this metal tang here is its
anchor point. Stretch the spring further to speed it up or compress the
spring a tiny bit to slow it down. In this case, Iím burning a little too
rich so Iím going to add a tiny bit of speed to the top end. There we go.
I just bent it a tiny, tiny bit.
we go: Iím just going to put in my spark-plug after giving it a quick
check. Now you definitely may want to change your sparkplugs. Theyíre
cheap and sometimes if you have a no-start/no-run problem it could be as
simple as a dead plug. Itís such a common problem that if you still have a
no-start/no-run problem: itís not a bad idea to go get a second new plug
and make sure that the brand-new new plug that you just tried isnít also
- [Mower starts]
- OK now Iíve run the machine for an hour
after the tune up and Ė check it out. Itís starting to whiten. OK,
itís obviously hotter over on this side, you can see that. Spark is hotter
on that side but itís starting to whiten up which means somethingís
worked. Either the tune-up or the raising of the operating speed has leaned
out the mixture enough that weíre starting to get a nice clean burn.
copyright © 2010 - 2011
* Repairs101.ca * All Rights Reserved.