The GZ is a simple bike with few real problems but still needs TLC just like other bikes. You may want to go through the entire fuel system. Clean the tank out. Do the carb as needed. Remove and check the petcock and replace hoses(vacuum and fuel) to the carb and petcock. While you are at it add an inline fuel filter.
Clean all switches and contacts, side stand switch included. The tires are likely junk by now so plan on a replacement for them soonest. I would personally add new tubes too.
Check out the chain for frozen links, wear on sprockets and chain also.
Check out the brake pads up front and brake shoes in the rear while the wheels are off for the new tires. AND be sure to change the brake fluid too.
Make the bike as safe as possible for your riding pleasure and safety.
Oh, just had another item to the list. Change all the bulbs for the signals, brake light, headlight etc. After this many year the bulbs will be less bright and will be unreliable.
Keep us updated on your progress.
