How do you service front fork oil on 1966 Yamaha YDS3 motorcycle?

To service the front fork oil on a 1966 Yamaha YDS3 motorcycle, first, remove the front wheel and fender to access the forks. Then, loosen the top caps and drain the old oil by inverting the forks. After letting them drain completely, refill with the recommended fork oil to the specified level, usually around 5-6 ounces per fork. Finally, reassemble the forks, ensuring the caps are securely tightened.