Henry,
Plugs will change color "very" quickly. Obviously, if you have one
that is stained from fuel additives, has spots on it from metal
transfer, or an excessive buildup then it should be cleaned, blasted
or replaced. However ......... when we casually pull plugs just to
"take a look" we are really looking at our pilot mixture as that is
where we are most of the time. If you let the bike idle for very long
before looking you will be seeing the pilot mixture with the throttle
plates closed ..... If you want to make a better judgement on a main
you should make a blast at full throttle, pull in the clutch, cut the
ignition, coast to the side of the road and pull them ... they change
that fast.
Obviously, there are usually other indications that will support what
you find anyhow ... IE .. you start getting a really irritating
vibration at 3000 - 3500 RPM at steady throttle but it is OK when you
give it a little throttle ..... then your pilots are too lean .... you
casually ride home and pull the plugs you will probably find the main
body "white" etc ...... If you put a main jet that is entirely too
large in the bike and cruise around ... using moderate throttle you
will not see this impact the plug color ... you need to exercise the
area of operation you are interested in immediately prior to looking
at them.
I expect plug color from a casual pull to indicate light/moderate
throttle cruising but the findings are even more useful as an
indicator of general engine condition. Of course you want to see the
nice tan to slightly dark tan color described in the plug reading
charts but you really want to look for significant differences between
cylinders. Finding a significant difference between plugs that can not
be adjusted out with a minor pilot mixture screw adjustment is an
alarm and should be addressed.
When you think you have your engine in good tune .. and plug change
time rolls around, (I change with every oil change), mark the mileage
and date on the new plug boxes and put the old set in there ... throw
them in a drawer somewhere. You will find that when you decide to
change things down the road or have some difficulty it is always nice
to look back and see what they "used" to look like when things were
"good", (might save you from fixing something that really does not
need fixing). Of course .. since I know "everyone" is syncing their
carbs and taking a compression reading, (hey .. we had the plugs out
anyhow !!), when doing this servicing, (oil/filter change), this is
actually a good time to "write down" the compression and vacuum
readings that are obtained for the same reason. IMHO as always .......
campbell
----- Original Message -----
From: "Henry Jackson" <[EMAIL PROTECTED]>
Subject: Re: reading plugs
> ----- Original Message -----
> > The "electrode" color doesn't matter .. it will usually
> > be "light" ........ the porcelain body is what you want
> > to look at.
>
> So after you make a change to the fuel/air mixture,
> how many miles do you need to run before the plugs will
> give you an accurate reading? Or do you need to install
> a new set of plugs and then run how many miles?
> snip <
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