I just picked up a set of used shocks for my 400F and am considering trying this. What's the worst that can happen?
http://www.superhunky.com/Saveshocks.htmlSave Those Old Shocks
Do It Yourself Tech
Nov 1, 2005
By: Rick Sieman
Rebuilding Those Non-Rebuildable Units
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 1½ 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 ¼ - 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 ¾-ounce automatic transmission fluid mixed with ¾-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.
