The rule here is simple: Grease your bearings.
New dirtbike buyers pick up this habit early, since many motocross bikes
roll off the showroom floor already needing a healthy slathering of grease
in areas such as the steering-head bearings and suspension linkages. But
street riders need to keep their bikes lubricated, too. While the sealed
bearings on modern streetbikes are relatively maintenance free, exposed
areas such as suspension linkages need routine care.
Even if you grease religiously, the time will come when you'll have to
replace key bearings. So check them periodically.
You can test your steering stem bearings by raising the front wheel off
the ground with a stand. If you feel any notchiness when you turn the handlebars,
or notice any play when you push on the fork back and forth, replace the
bearings.
Likewise, if you feel any play around the front or rear axle, the wheel
bearings need to be replaced immediately.
Another critical pivot point is the swingarm. It shouldn't move side-to-side.
The scary thing about bearings is that when they start to go, they go
fast—sometimes with catastrophic results. Never put off replacing a bad
bearing.
Also in the lubrication category, many bolts benefit from a bit of anti-seize
coating when re-installed. Examples include the axles, swingarm bolt, linkage
bolts and motor-mount bolts.