Thanks to Wayne Tucek for suggesting this tip!
Early 'Wings have very robust driveshafts, but they do fail occasionally. The most common failure point is the u-joint on the front of the shaft where it joins the transmission output shaft. The rear splines that join the rear coupler can fail, but that's very rare.
Honda made numerous running changes during production. Early '75 models (without the lube zerk near the final drive unit) were somewhat prone to premature failure, but Honda was quick to correct this.
Warning signs:
1. Rythmic "clicking" sounds that directly correlate to road speed (not engine rpm)
2. Excessive driveline slack
3. Harsh vibrations
You can wait for catastrophic failure or you can implement an easy inspection procedure for early detection of driveshaft problems.
Be aware that u-joint problems don't linger. They rapidly accelerate to total failure. In additional to stranding you, a failed u-joint can cause major collateral mechanical damage as well as loss of control and crashes. Not something you should ignore!
I recommend the following 10-minute inspection as an annual ritual. It's a good thing to do whenever you do tire or brake work as well.
Inspection procedure:
1. Place the bike on the centerstand
2. Pull the rubber driveshaft boot toward the front of the bike for access to the u-joint.
Shown are some boot removal and installation tools. A cotter pin removal tool (above) works very well. An old-fashioned brake adjusting "spoon" works too. In a pinch, a broken and bent flat screwdriver can be pressed into service. Needle-nose pliers and a long drift are useful "persuaders" as well.
3. Turn the rear wheel forward and backward to inspect the u-joint.
4. U-joint problems can usually be seen, felt or heard and are typically obvious. Look for any appreciable "lost motion" or lurching of the joint. You can get fancy and put a dial indicator gauge against the joint to check for abnormal runout, but that's usually overkill.
5. Important: using a small pocket magnet, check inside the boot for metal particles. If any metal is found there the u-joint is almost certainly going bad! This is the key aspect of this inspection procedure.
6. Look for smooth, worn shiny spots on the yoke surfaces. This indicates metal to metal contact and joint failure. See the example indicated with the red arrow:
7. Severe failure will reveal gouged areas on the yoke as indicated with the blue arrow:
8. If no problems are detected, reposition the rubber boot taking care not to puncture or tear.
This procedure is easier on a warm day when the rubber boot is more pliable and cooperative.
These driveshafts are considered "non-rebuildable," but with the help of my friend Bob Hagerman, we're working to overcome that!
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