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MC How-To

Step by step: From general maintenance to complete restorations, we share tips and tricks for working on classic bikes.


Replace Honda CB450 Swingarm Bushings

Honda CB450 swingarm bushings have a reputation for wearing out prematurely. Early CB450s like our subject 1970 CB450K4 used metallic bushings, while later ones apparently switched to plastic, a material more than a few manufacturers embraced for ease of installation.

Whether early or late, CB450 swingarm bushings don’t appear to last more than 10,000 miles or so. Our subject bike doesn’t appear to have led a particularly difficult life, yet with a mere 13,000 miles showing on the clock the swingarm bushings were shot, exhibiting an easy 1/8 inch or more of slop on the swingarm pivot pin. Although a small amount of play won’t show adverse effects, too much results in a wandering rear end, the back wheel moving left and right, generating an uncontrollable steering input. Typically, once the wear becomes great enough to notice, it accelerates rapidly.

As originally fitted, the swingarm on the CB450 (and many other Hondas, including the CB500T, CB500 and CB550 Four and all pre-1979 CB750s) had a single bushing on either side of the swingarm followed by a felt sealing washer, a thrust bushing and an outer metal dust cap. Original replacement bushings are still available, but experience shows that if you’re actually riding your bike you’re wise to consider fitting aftermarket bronze bushings like the ones we sourced from Honda specialists Charlie’s Place.

The bronze bushings from Charlie’s Place do away with the felt sealing washers and the thrust bushings, and at $70 a set they are only marginally more expensive than stock (typically around $55-$65 for bushings, thrust bushings and felts), and thanks to their superior material it’s unlikely you’ll ever replace them again. BikeMaster

Better yet, the bronze bushings are very easy to install. The factory bushings have no shoulder, requiring the installer to ensure they’re properly inserted to the correct depth inside the swingarm. The bronze replacement bushings are shouldered, making insertion installation much easier: Just press them in until they seat.

While installation is easy, the old bushings can be difficult to remove, particularly the early metallic style, which can become seemingly welded to the swingarm. The solution is often to cut them out or press them out with a hydraulic press, if available. Thankfully, ours removed quite easily using nothing more than a hammer and a blunt punch.

As we show, installation is a snap, but you might have to give the bushings a quick pass with a small brake cylinder hone to get a proper fit for the swingarm pivot. The bushings are a light interference fit with the swingarm, so they tend to compress slightly. If you have to hone them, do so in short passes, checking the fit of the swingarm pivot pin frequently. You don’t want to remove any more material than necessary for the pin to slide into place.

This is a fairly straightforward job, easily within reach of the average weekend mechanic. The only special tools you might need are a small 3/4-inch to 2-inch brake cylinder hone and a torque wrench for final tightening. Budget a morning to get the job done, and as always, we recommend having a good shop manual on hand for parts identification and proper torque specs.

 

1. Put the bike on its centerstand. Disconnect the chain. Disconnect the brake stay at the brake hub. Disconnect the rear brake actuating rod. Remove the rear axle cotter pin, loosen the axle nut and then remove the rear axle and finally the rear wheel. Remove both lower shock absorber mounting bolts.

2. Remove the swingarm pivot bolt nut on the left side of the swingarm.

3. The end of the swingarm pivot bolt is dimpled. Using a suitably sized punch, gently knock the pivot bolt through the swingarm. Remove the bolt.

4. With the pivot bolt removed, pull the swingarm straight back and free of the frame. To give ourselves a little more working room, we removed the left shock. Although we didn’t, removing the chain guard simplifies chain installation.

5. Once the swingarm is free, remove the dust caps and thrust washers (thrust washer pictured). Set the thrust washers aside; you won’t use them with the new bronze bushings.

6. Next, using a suitable drift, remove the swingarm pivot pin. It should knock out easily, but accumulated grease, dirt and corrosion can make it a little stubborn to remove.

7. Here’s our pivot pin after knocking it out of the swingarm. Thankfully, it cleaned up well, as replacements are getting quite difficult to find.

8. With the pivot pin knocked free, remove the felt sealing washers at either end of the swingarm and discard them. The new bronze bushings don’t use these.

9. Next, remove the old bushings. Ours pushed out fairly easily using nothing more than a blunt-ended punch and a hammer, but they are known to be difficult to remove, sometimes requiring a hydraulic press to push them out or a hacksaw blade to cut them out.

10. Here’s one of our old bushings removed from the swingarm. Before moving on to installing the new bushings, clean any debris or grease from the inside of the swingarm tube.

11. Next, install the new bushings. We pressed them in using a simple homemade tool made up of a piece of all-thread rod, with washers and nuts at each end, steadily tightening the nuts until the shoulders of the bushings seated against the swingarm.

12. Here’s one of the bushings fully seated in the swingarm. With the new bushings installed, we found the swingarm pivot pin to be a tight fit.

13. To make the swingarm pin a sliding fit in the bushings, we lightly honed them with a small brake cylinder hone, removing only enough material to allow a tight sliding fit. After honing, thoroughly clean the bushings with brake parts cleaner.

14. With the bushings honed, our swingarm pivot pin (visible inside the bushing) slipped into place. With the pivot pin installed, lightly grease the dust caps and install them on either side.

15. Using a grease gun, push the old grease out of the swingarm pivot bolt until only fresh grease comes out of the lubricating holes in the bolt.

16. Push the swingarm back into place in the frame, then insert the swingarm pivot bolt through the swingarm from the right side.

17. With the swingarm pivot bolt in place, thread the pivot bolt nut onto the bolt and then torque it to 51-65ft/lb. We went for the middle of the range, 58ft/lb.

18. Next, using a grease gun, grease the swingarm pivot until fresh grease just starts to show around the dust caps. Reinstall the rear wheel, the drive chain, the brake stay and the brake linkage. Adjust the chain as necessary and tighten the axle nut, making sure to reinstall the cotter pin.