Honda 2012 TRX420TM Owner's Manual page 153

Worn brake pads should be replaced. If the pads are not worn, have your
brake system inspected for leaks.
Other Inspections
Make sure there are no fluid leaks.
Check for deterioration or cracks in the hoses and fittings. If the hoses
are worn or cracked, have them replaced by your dealer.
Brakes
Servicing Your Honda 145