2001 Yamaha YFM660 Raptor Factory Service Manual, Page 325Get this manual
OVERHEATINGOVER COOLING FAULTY BRAKE OVERHEATING OVERHEATING Ignition system Improper spark plug gap Improper spark plug heat range Faulty CDI unit Fuel system Improper carburetor main jet (improper setting) Improper fuel level Clogged air filter element Compression system Heavy carbon deposit
TRBL SHTG
Engine oil Improper oil level Improper oil viscosity Inferior oil quality Brake Brake drag Cooling system Low coolant level Clogged or damaged radiator Damaged or faulty water pump Thermostat stays closed