Keep Your Bolts Bolted
It’s truly a marvel that the clockwork cacophony of motorcycle parts—all designed, manufactured, and arranged so precisely—hold together and continue to function for thousands and thousands of miles. However, something as simple as one bolt coming loose can absolutely wreck your engine or other critical system on the machine.
As such, calculations have been conducted on every single nut and bolt on the unit to ensure that everything stays in place and functions properly. Usually, tightening a fastener to the specified torque is enough, but in some cases, such as under high vibration, high rpm, or "permanent" installation applications, you need a bit of additional security in the form of a special type of adhesive called a threadlocker.
Components that experience more vibration, extreme rotational forces, extreme heat, thermal cycling, or are constantly exposed to oils often use threadlocker to keep bolts in place and torqued properly. Threadlocker is also used for an additional layer of safety on critical safety components.
These adhesives are typically categorized by strength and are color-coded respectively. The flavors are generally, low, medium, and high strength.
Although it isn’t a hard and fast industry standard, the color codes are usually blue for low, purple for medium, and red for high-strength or "permanent" applications. There is also a wide variety of brews within the above-mentioned general classes formulated for specific applications, such as additional chemical/oil resistance or for use with specific materials.
In the Real World
Naturally, the different types of threadlocker are used in different applications and environments. You'll see the low and medium-strength varieties used for things like smaller bolts that do not experience extreme vibration or exerted forces.
They’re also good for parts likely to be removed for repair or maintenance work. Think clutch spring retaining bolts to ensure engine vibration doesn't work the bolts loose, or brake caliper bolts where the threadlocker provides an additional layer of security instead of vibration mitigation.
The strong stuff will usually be found in places that experience extreme forces, vibration, or heat, like internal engine components. In general, unless you're doing some pretty in-depth work, the average motorcyclists won't come across the high-strength goo all that often.
When you do, though, it's important to remember that the strong compounds are usually marketed as "permanent." This means that you’re likely to damage threads of break components with high-strength threadlocker applied to them if you try to remove a fastener with brute force without first heating it with a torch to melt and break down the adhesive.