1983 Yamaha YZ490 Service and Repair Manual

Restoring a 1983 YZ490 means working from LIT-11626-03-75, the factory manual Yamaha produced for the model coded YZ490K.

Engine coverage gives the original piston and bore dimensions, clutch and transmission procedures and the case-splitting sequence, along with carburetor settings and ignition timing as specified when the bike was new. Chassis chapters take in fork and rear shock service, wheel and brake work, bearing replacement and the frame torque values.

There is no substitute for these numbers on a machine of this vintage, where guesswork and aftermarket parts have had four decades to accumulate. Check the frame stamping reads YZ490K, then work from LIT-11626-03-75 rather than from a specification remembered off a forum thread. Where the bike differs from the diagrams, you have at least learned what a previous owner changed.