These are some things we have seen and examples of why it’s important to carefully inspect items while servicing and repairing power sports vehicles, some are more obvious than others.
Cracked frame, not from a crash but hours of stressful operation.
Chipped transmission gears.
This is when a chain guide is worn out and not replaced, now the swing arm is severely damaged.
Hard to see but the brake rotor is cracked.
This is a generator rotor that was starting to come apart and rubbing on the stator.
This water pump shaft has worn to the point it has grooves in it, reusing this would cause the seals to fail soon after replacement. A new shaft with new seals is the only way to go.
Never skip inspecting a screen type oil filter, in most cases they will be clean but this one caught a piece of broken clutch plate that was floating around in the bottom end of the engine.
A nice example of why you need the correct amount and type of oil in your engine.
If the a fuel tank does not flow fuel check the fuel strainer, it may look like this.
Here is a failed neutral/gear position switch. This was on a Suzuki Eiger and was causing the ECU to think it was in reverse all the time and limiting the engine RPM while going forward. This condition has been misdiagnosed as a carburetor issue as it sounds similar but is an electrical problem.