Got a good old
vintage bike and can't afford some trick new aftermarket shocks? Or
maybe you've just bought a tired (well-used) trail bike and see that the
shocks are non-rebuildable and feel like there's not much damping in
them.
There is a way
around all of this, and the best part is that it'll take just a little
bit of work and no money at all.
First, some
background. Most of the dirt bikes of the vintage era (mid-60s thru the
mid 70s) came with non-rebuildable shocks. Just about all of the bikes
from England were equipped with Girlings, as were many of the other
European brands. The Japanese bikes of that era were pretty, and not
much else. Honda and the other Big Four seemingly concentrated on
chroming the springs and ignoring the performance.
So, at that time,
the Girlings were state of the art, and with the limited short travel,
did the job and did it well. A large number of spring rates were also
available and the damping was correct for the application.
Their biggest
drawback was that they just don't last long and cannot be rebuilt. A
serious MX competitor could expect a set of Girlings to last
approximately two to three months at the most. The top desert racers got
about four races and then replaced them. The average rider, with a
little luck, got about six months of service before they were shot.
Girling did make some rebuildable shocks, but they were not available in
this country.
"PRIMING"
THE SHOCKS
There are two ways to extend the life of Girlings, neither of which will
cost you any money. The most important method is something called
"priming" the shocks. When bikes are stored for any length of
time, the longer they are stored, the more air leaks into the internals.
Even the smallest amount of air can damage the sensitive internal
damping mechanism.
When you buy a new
shock, or get a bike that's been stored for a long period of time, take
off the spring and gently pump the shock up and down for about 20
minutes. The air bubbles will then pass out of the oil passages. After
priming, the shock can be reassembled and used.
If the shock is to
be stored any length of time off the bike before using, do not lay it on
its side; instead, hang it up by an eyehole in the normal position. In
this way, less air will enter the internals. Priming will at least
double their life span.
THE FIX-IT
METHOD
The second method is to replace the oil after the shock has worn out.
When the shock is done for, oil will have leaked out and all internals
will have loosened and worn slightly. Make provisions to put fresh and
heavier oil into the shock, thereby giving it a second life. And a
third, and so on, if needed.
After removing the
shocks from the machine, take the springs off and set them to one side.
If they are sacked, they must be replaced. A good way to check this is
to compare them visually with new springs. If they're shorter, they will
need to be replaced.
Clean the shock
thoroughly before attempting to work on it. Make a mark three-eighths of
an inch from the base, making sure that the mark is facing outward from
the normal position on the machine. It will be necessary to use a punch
lightly to start the drill. Using a 3/16 inch drill bit, carefully drill
a hole in the shock base through the nut.
The trick here is
to keep any stray metal chips from falling into the shock. It works best
if the shock is laid on its side during the drilling. Clean as you go,
drilling slowly. Don't penetrate any deeper than needed; the internals
can be damaged by poking a drill bit indiscriminately. After the hole
has been drilled, clean the area and check for burrs.
The shock can then
be drained of the old oil. There should be about 1? ounces drained out
of a typical 12.9 inch Girling. If less comes out, it just means that
some oil has leaked out over the years.
Hunt through your
tool box and find a ? - inch, 28-thread nut and bolt. Clean this
thoroughly, then weld or braze the nut near the base of the shock. Make
sure that the shock is fully extended when welding A word of caution:
get the oil out of the shock first before welding the nut on, as we have
heard tales of old timers literally blowing a shock apart from burning
oil. Got that?
FILL 'ER UP!
Your new oil should be mixed carefully. The best ratio is ?-ounce
automatic transmission fluid mixed with ?-ounce 20-weight motor oil.
You can also add a tiny bit of alcohol to soften seals and O-rings. A
3-in-1 oil can with the bottom cut off makes a great funnel for
refilling. It will be necessary to stroke the shock up and down to get
all of the oil in.
Install the bolt
in the nut and tighten down firmly. The fine threads should guarantee
against leaks. If leaks are encountered, use a red fiber washer. After
the bolt is in place, prime the shock again and install.
The shock will
eventually wear again. It is then a simple matter to remove the bolt,
draining and putting in a slightly heavier oil. The heavier oil will
make up for the worn O-rings and seals. Some riders have run as heavy as
a straight 30-weight oil, and the shocks are still functioning well.
Once you get to the point where 30- weight won't do the job, then the
Girlings are truly ready for the trash can.
This technique not
only works well for Girling, but other non-rebuildable shocks as well.
|