Try the diagrams at Partzilla. That would be a start.
Then search eebbaayy for Kawasaki G5 carburetor & try other searches.
I saw one used carb for the G5 & one new listed for various vintage Japanese motorcycles, including the G5.
Air Striker PWK 38 Keihin 38mm. about $95 shipped.
The Kawasaki service manual may list the carburetor. There might be a G5 manual on eebbaayy.
If you happen to have the owner's manual, that could be useful.
1981 KZ650-CSR. Competition, Sports & Road.