The Importance of Fasteners

We spent a lot of Sunday thinking about fasteners. In the morning, it became apparent that one of the well-made fairing bolts on our 1980 Honda Cub had come loose and fallen off on the road. Four bolts secure the fairing, so it was in no danger of coming off. Even so, the lost bolt raised the question of what torques had been applied to other fasteners while doing maintenance over the years, and which were backing off.

We use a torque wrench for axles, fork bolts, crank bolts and valve cover studs, but for a fairing bolt? Seems like too much hassle. It probably is too, but the bolt’s loss underlines the importance of regular checking of snugness and torque on fasteners across the bike.

It reminded us of the time we botched a fork replacement job. A fork tube on a ’74 Honda CB550 had been bent in a crash, and we purchased a torque wrench to help get the reinstallation right. The new fork went in without a hitch, and then it was time to install the front wheel. We looked up the torque values in the manual, set the wrench to the proper value, and set to work cranking down the axle bolts on the bottom of the fork.

Whoa! The torque wrench was calling for way more force (x distance) than we had ever imagined. It felt like we were learning lots with this new torque wrench. And then the first bolt stripped.

Our error? Not reading the right value from the manual. We had used the value for the “front wheel axle nut, 47.0 lbs-ft” instead of the “front axle holder nut, 8mm, 13.0-16.6 lbs-ft”! The bolt was destroyed; we disassembled the old fork tube and the new one and swapped the sliders. It was an expensive lesson.

If you are interested in learning more about fasteners and getting better at visualizing the forces inside them, head to motorcyclecruiser.com and read The Nuts and Bolts of Nuts and Bolts.