Changing Fork

The hydraulic fork is comprised of two sets of telescoping tubes that work against springs, with an oil filled (hydraulic) dampening mechanism to control the action. The unit is engineered to give long service with a minimum of repair. Oil change is not necessary unless oil has been contaminated or leakage has occurred.

To drain fork sides, remove fork tube cap as described in "Disassembling Front Fork." Remove drain plug (29, Fig. 2F-21) from lower end of fork slider. Loosen tube end nut or bolt (11 or 11 A, Fig. 2F-21) several turns. With a screwdriver move shock absorber up and down to loosen any sediment in bottom of fork slider, so oil will run free from drain.

After each fork side is drained and drain plugs have been installed, forks can be refilled by using an improvised filler can.

To make a filler can, see Fig. 2F-22, and proceed as follows. Drill a dozen 1/4 in. holes in the bottom of a one quart tin can (2), near the outside edge. Then, shape the bottom of the can with a light hammer so that it is dished upward to assure complete draining of oil through the holes.

Select a tin funnel (3) with the funnel mouth about the same size as the bottom of can (2). Swage and shape the funnel spout, so that a piece of 1/4 in. metal tubing (4), about 2 in. long (a piece of fuel line is suitable), can be soldered into it. Solder (3) onto the bottom of (2). Improvise and attach bail (1) to the filler can.

Make plug (7) from a rubber bottle stopper purchased from a drug store. Rubber stopper should be 1 in. to 1-3/8 in. long, and its largest diameter about 5/8 in.

Hold rubber stopper in vise and drill a 3/32 in. hole lengthwise through the center. Then enlarge the hole with a 1/4 in. drill. After hole is drilled in the stopper, insert a 1/4 in. rod (6) through the hole and grind the stopper to a 5/8 in. diameter at the large end, and slightly under 1/2 in. diameter at the small end, straight taper between ends to form the plug.

Slightly flare one end of a piece of 1/4 in. tubing (6), about 2 in. long, and insert into plug (7). Make an adapter (8) from an old fork tube cap, Part No. 45757-49. Break three stake locks securing breather valve and remove valve from cap. Drill a 1/2 in. hole through cap and plug the vent hole. Assemble adapter (8) to top of fork and insert rubber plug (7) into the adapter hole. Attach filler can to stopper with transparent flexible tubing (5) about 2 feet long.

Suspend filler can above motorcycle so that when improvised fork tube cap is assembled in fork filler opening there will be ample slack in flexible tubing to allow fork to work up and down without tubing becoming taut (see Fig. 2F-23).

Pour correct amount of fork oil into can, 1967 and earlier: (3-1/2 ounces in each fork side after draining; 4-1/2 ounces, if fork has been completely disassembled or flushed with a solvent and is dry.) 1968 and later: (4-1/2 ounces after draining or 5-1/2 ounces assembled dry.) The difference in the amount of oil required between a (DRY) and a (WET) fork is due to oil cling. Do not use more oil than recommended because the excess oil will cause leakage from the top of the fork tubes.

Work the fork up and down. Air escaping through oil in filler can as fork is pushed downward will cause the oil to bubble violently, but because the bottom of the filler can serves as a baffle, no oil will be lost. As the fork moves up, oil will be sucked into the fork side. Usually working fork up and down 3 or 4 times is sufficient to empty filler can. After filler can appears to be empty, it is good practice to allow a few seconds for can to completely drain into hose, then work fork once more. This assures getting all oil into the fork side.


If the hydraulic fork does not work properly or an appreciable amount of oil leakage should develop, inspect the fork as follows:

Check the oil level in each fork side by completely draining and refilling fork as described in "Changing Fork Oil." Insufficient oil in either fork side will result in faulty recoil action and excess oil will cause leakage from the top of fork tubes. When checking oil level in each fork side, also check for water in fork oil which will cause leakage from fork tube cap or oil to bypass fork slider bushings. Oil will appear emulsified, aerated or light brown in color.

If the fork does not function correctly after eliminating the possibility of water contamination or fork oil and incorrect oil level in fork sides, inspect the fork tube breather valve (2) for defective condition. Remove fork tube cap (1), submerge in water and blow compressed air through cap vent hole. Breather valve should not leak below 15 lbs. air pressure. If breather valve is faulty, renew valve as described in "Replacing Breather Valve."

If snubbing action of the front fork remains unsatisfactory, bottoms on compression, stops suddenly on recoil and does not operate smoothly after eliminat-

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