Pretty much any problem that arises with the way your bike turns or tracks or handles will be the result of something breaking, wearing out, or wandering out of specification. If something breaks, the change will be sudden, while other issues may be progressive and worsen over time.
Far and away the most common handling problem that people encounter is heavy, high-effort steering. If you find that you have to use a lot of muscle to initiate a turn and then you have to keep pressure on the grips to hold your line through a corner, the first thing you should check are your tires. A worn profile will cause this kinda handling, but so will underinflated tires, even if they’re just two or three pounds.
Another complaint we hear from the MC Garage audience is about a bike that doesn’t want to track straight. That might mean it weaves down the road or even pulls to one side. If that’s the case, the first thing you want to verify is that your wheels are aligned, and if you have spoke wheels, check to see that there aren’t any loose ones. Loose steering head, swingarm, or wheel bearings could also be the culprit. But don’t confuse an actual instability issue with “tramlining,” which is when your bike’s tires follow grooves in the road. We have grooved concrete on the highways here in SoCal, and it can make it feel like there’s a ghost steering your bike. There’s nothing you can do about that except relax and let it happen, or take a different route.
If your bike is vibrating a lot more than it used to, someone may have swapped your multi-cylinder bike out for a single, or a major bolt may have loosened up. Better put a torque wrench on the nuts and bolts that secure the engine to the frame. If, however, it feels like the vibrations are coming from the wheels, you may have lost a wheel weight, a wheel might be out-of-true, or there may be something wrong with your tires. Check your tires for bulges or damage and spin your wheels to see if they’re still straight.
Next up, ride quality. If your bike has gotten more sensitive to bumps and is feeling harsh, your suspension may be binding. This is something that’ll happen progressively as fork bushings wear and the oil gets dirty, or as the swingarm or suspension-linkage bearings dry out and seize. Or, you might just have over-inflated tires which can make for a rough ride.
Finally, a handlebar or clip-ons that start to wobble as soon as you loosen your grip can be pretty unnerving, but it’s not uncommon. Front-tire wear is often the perpetrator, but some of the previously mentioned issues, like loose head bearings or improper tire inflation, can cause this sorta issue too. In the end, most of these handling problems can be avoided by performing basic maintenance and safety checks.