Step by step: From general maintenance to complete restorations, we share tips and tricks for working on classic bikes.
Top to bottom: new fork tube and components; pitted fork tube and old bushings and seal, fork spring and damper assembly. Photo by Motorcycle Classics staff.
Fork oil is not supposed to be gray, but this kind of contamination is pretty common. Photo by the Motorcycle Classics staff.
Positioned as they are at the front of the bike, forks end up by default with heavy exposure to road debris and moisture. Dirt and moisture take a toll on fork seals, which help keep fork tubes clean, wiping them with every pass. And while keeping the fork tubes clean helps, once the tubes become pitted there’s nothing left to do but replace both the fork tubes and the seals.
This How-To centers on rebuilding Roadholder forks on a 1974 Norton Commando. First introduced in 1946 and then modified in 1953, Roadholder fork construction stayed relatively constant until the end of Norton production in the mid-1970s. A robust design — a fact echoed by their long production life — they’re generally easy to service, with the typical overhaul involving a full strip, followed by a thorough cleaning and seal replacement. There can be other issues, such as fork tube bushing wear and fork tube wear from years of use.
The tubes on our Norton were badly pitted, so we bought new fork tubes, as well as new bushings. That turned out to be a good call, as the upper bronze bushings were in poor shape. The lower bushings are hardened steel and tend to last much longer, although we replaced those, as well.
A project bike purchased by managing editor Landon Hall, our subject Norton hasn’t turned a wheel in 20-odd years, and with zero history on the bike, it was anybody’s guess what we’d find once we started.
What we did find was a high degree of moisture contamination and resultant sludge, the damper valve and damper tube cap on one fork being particularly grungy. Fortunately, they cleaned up fine and are perfectly serviceable.
We also found worn steering head bearings, and with the front end already torn down it was time to replace them. Commando steering yokes turn on two sealed bearings press fit at the top and bottom of the steering head tube, with a spacer tube in between. Replacement is typically straightforward, but moisture contamination reared again as we discovered the steering stem was practically rusted to the inner bearing races. It took patience, but with a combination of penetrating solvent, a heat gun and a good hammer, we finally convinced the steering stem to break loose. Note: Never hammer on the stem without first threading the securing nut until it’s just flush with the end of the stem to prevent thread damage. Further, never hammer on the nut and stem directly; use a block of wood.
This isn’t an expensive proposition. Excepting fork tubes (not always necessary), expect to spend around $75-$100 on parts, with everything readily available from your favorite British parts supplier. If you do need fork tubes, add $110-$200 (prices vary depending on the maker and supplier) to the bill. Head bearings, purchased locally, cost us a further $23 for the pair.
This is an easy weekend job, but as usual we suggest taking your time. Budget four to eight hours total including initial teardown and final reassembly. As always, we recommend having a good shop manual on hand for parts identification and proper torque specs.
1. Support the front of the bike. Remove the front wheel, brake caliper and fender. Unbolt the headlamp shell from the locating ears. Disconnect speedometer and tach drive cables and instrument lights. With a 1-5/16in socket, unscrew the top chrome-plated fork caps.
2. Lift the fork leg enough to expose the top of the spring. Hold the nut securing the spring to the damper rod with a 1/2in open-end wrench. Loosen and remove the fork cap.
3. Loosen the pinch bolt on the lower steering yoke. You can drain the fork oil now by removing the drain screw at the bottom of the fork leg or pour it out once the fork has been removed.
4. The top of the fork tube is a taper fit to the upper yoke. Screw the fork cap back into the tube at least 5 turns. Hold a block of wood on top of the cap. Strike the wood with a hammer to break the taper. Remove the fork assembly.
5. Clamp the bottom of the fork leg in a vise and remove the threaded fork leg collar. Ours was seized. We heated the fork leg with a heat gun and finally broke it loose with a pair of C-shaped pliers. A strap wrench is preferred to avoid damage, but our collar was stuck fast. Fortunately, it came off clean.
6. Remove the fork leg from the vice and using a 1/2in socket, remove the damper rod-securing bolt.
7. Pull the damper rod assembly out of the fork. Note the fiber sealing washer at the bottom where it joins the fork leg. This must be renewed. Remove the nut holding the spring to the damper rod. Remove the spring. Clean all parts thoroughly in solvent and dry.
8. The damper rod assembly on the left fork was covered in sludge from moisture and dirt contamination. If necessary, remove the aluminum top cap on the damper rod tube. Separate the damper rod from the damper rod tube and clean all parts thoroughly. Reassemble the damper rod with spring.
9. Next, secure the fork leg in a vice. Push the fork tube in fully, then pull back sharply to knock the upper bushing complete with seal loose from the leg. Remove the fork tube. This photo shows the major fork components, with the fork leg in the background, followed by the fork tube and finally the damper rod assembly and spring. The lower fork tube bushing is steel, the upper bronze.
10. If replacing the lower fork tube bushing, remove the circlip at the bottom of the tube. Remove the bushing. Install new bushing with new circlip.
11. Clean fork leg thoroughly and blow dry with compressed air. Place new sealing washer on damper rod assembly. Install damper rod assembly, then the securing bolt. Torque to 10ft/lb.
12. Place the fork leg upright. Install the fork tube. Slide the new upper bushing down the tube and push into the fork leg. Next, slide the old bushing upside down over the fork tube. Use the old bushing as a slide hammer, rapping it against the new bush until it fully seats.
13. Next, place the thin paper gasket on top of the new bushing. Lightly coat the new fork seal with grease and slide it into place using hand pressure. Seat the seal using an old top bushing as per step 12.
14. Return the fork leg to the vice. Screw the fork leg collar back in place. Use a strap wrench to fully seat it. Install the rubber fork tube boots.
15. Slide the fork assembly back in place through the steering yokes. Lightly secure with lower pinch bolt. Make sure the drain screw is secure with new fiber washer. Slowly fill the fork leg with 150cc of fork oil.
16. Once the oil has settled, push the fork leg up far enough to place the instrument over the spring, followed by the fork cap washer. Thread the fork cap onto the exposed damper rod shaft until it seats on the spring retaining nut. Hold the nut with a 1/2in wrench and tighten the fork cap to lock it to the shaft.
17. Push the fork cap down. Slowly turn counterclockwise until you feel its threads engage, then turn clockwise and thread into the fork tube. Loosen the lower pinch bolt. Position instrument and tighten the fork cap.
18. Reinstall the front wheel and fender. With the bike off the stand, firmly push down on the front forks several times to center the steering yokes. Tighten the fork caps to 35ft/lb and the lower yoke pinch bolts to 10-15ft/lb.