Bike not starting

Hello everyone, so new to bikes bought my first bike its a 1981 Kz650 H1 csr. based on everything so far it seems its old connections and wiring that keeps it from staring on its own (I had it connected to a car battery and it started, yes I won't be doing this again). From the dude I bought it from carbs were cleaned and had new spark plugs and battery. When the battery is charged and you try starting the bike, and I am trying the correct way, choke open, clutch down and not pulling the throttle, that starter motor works bike just doesn't start and it is getting fuel. So giving all that I'm hoping for some input and knowledge also if there's a place I can get a newly made wiring harness that I can just plug and play with hopefully to get the biking running.

Welcome. My wiring is 40 years old. Chances it's something simple. Pics would help sorting out the wiring.
Steve

It could be a weak battery. If it does not show over 13VDC with no load, and if it will not pass a load test, it is toast. Many automotive parts stores will do a load test for free.
The ground cable from the battery to the engine or frame is often corroded. Make sure it is clean at both ends and making good connection.
A can of Deoxit, some cotton swabs and and small brass brushes will be a big help in getting all those old connections properly cleaned.

There are several good tutorial posted here by member MFolks. Do a little search and read. A genuine Kawasaki Factory Service Manual (fsm), an analogue volt-amp-Ohm meter and an afternoon of quality time with the wiring will get it up to snuff.

By the way, when starting a cold motorcycle or carbureted car, the choke should be closed (on), not open (off). Oh, and I think the 650s have enricheners rather than chokes.

How do you know it is getting fuel?

when the bike was connected to my buddies car we started it and it stayed running plus I took the spark plugs out and I can smell gas

Ok.

When connected to an external battery, the bike starts and runs as it should.

When using only the bike's battery, the starter turns the engine, but it will not fire. (I have made an assumption here. Is the starter turning the engine, or is it freewheeling?)

That suggests that not enough power is getting to the coils while the starter is engaged.

That most often is due to a weak battery and/or corroded or loose electrical connections.

Yes another person had suggested that also, someone suggested running a wire from the battery to the coils and seeing if it starts. Good that someone else thinks this I also think its just the dirty old connections so I'm going to get new spark plugs and battery and try that wiring and seeing what goes if its starts then I should need to clean up the connections and the wiring harness or even think on getting a replacements will keep yall updated