Basic Spark Plug Questions

 I think I'm going to replace my own spark plugs.  This is major rocket
surgery for me.  The valve clearance procedure also looks pretty easy, and I
don't need any help on that ... yet.

Spark plug questions:

a)How do I remove the wires?  Grab the rubber thingies close to the plug and
pull?  Anything I can do wrong?  (This is a serious question -- I'm not
joking -- I've never done this.)

b)When replacing the plugs, for new plugs it says to seat it and then turn
some fraction of a turn, but for used plugs (putting your used plugs back
in) it specifies a torque.  Why the difference in specification for new vs.
used?  (What I would actually do for new plugs is follow the "so many
degrees past seating" instruction then put a torque wrench on them just to
be sure that are at least that tight.)

Thanks.

 David T. Ashley wrote:


Not familiar with your bike(s), but mine just pull off. Twist/rock
gently with a bit of pressure. No forcing.


Turn in the plug by hand until it seats. Put the socket on it and turn
an additional eighth-to-quarter-turn. Do please place a light coat of
anti-seize on the plug's threads first. New or re-used plugs.

--
   -bts
   -Motorcycles defy gravity; cars just suck

 
This is going to be good stuff!  Rocket surgery soon coming.  Watch for the
news article about "Motorcycle Spontaneously Combusts in Marshall,
Michigan".

 

Careful about the wires, some bikes have plug caps (I'm assuming at some
point the motorcycle industry caught up with modern technology) and those
plug caps can come out.  No big deal, but you have to make sure you seat
them properly or you won't get good spark.

As for torquing the plugs, the danger there is overtightening them - it can
happen and you can strip the cylinder head.  I never torque plugs, I hand
tighten then give a final snug with the wrench to seat them.  They're spark
plugs and they aren't any different than the ones on your car.  Your bike
may use crush washers, which may be the reason for the different
installation method.

 
A new spark plug's sealing washer is not flat in cross-section;
turning it the specified number of degrees crushes it. You don't use
torque here, because the torque reading will be thrown off by the
washer being deformed.

On a used plug, the washer is already squished flat so tightening the
plug will create tension on the threads instead of the washer. This is
where you're likely to strip things. Fortunately, since you're no
longer deforming the metal washer, a torque wrench will read
accurately in this case.

I don't bother with a torque wrench on a used plug. I hand-tighten,
then turn maybe 1/16th of a turn until it just feels right.... just
snug enough to not back out with vibration. You'll be able to feel the
resistance suddenly start to ramp up when you're there. I probably
under-torque them but it's way too easy to strip an aluminum cylinder
head, so too loose is better than the alternative.