TOPIC:

I was not aware that there was a filter on the return line. I have seen a few injected bikes use those plastic things on the delivery lines and they always pop. Many have the filter inside the tank so the engine just stops but others have gone up in smoke.
I am now wondering why the hell a filter is required on a return line.

It sounds fine to me, the idle is reasonably smooth. You'll get ticking from the injectors by the way, that's normal. That plastic filter is stock, it's not under any pressure as it's in the supply to the pump. Re. the oil light on that'll be the oil level sensor which is a known fault on the later models. If the oil light goes out after turning the ignition off & back on again & restarting the engine there's nothing to worry about as it's the oil level sensor. I tried cleaning mine when I had the sump off a couple of years back but it still plays up. I just do the ignition off/on thing to clear it every time I ride the bike.

Update,

I tried what Phil suggested the light doesn't go out, after shutdown ignition off then on the engine start.

On the other hand I found the Oil warning switch; Kawasaki seems to have moved it into the tail section for the ZG models. I Hooked up some wiring to test it was working correctly, and it seems that is the case. Rechecked the oil pressure sensor, on when no pressure and closed when bike is running. Also took it out to confirm oil pressure with a pressure Gauge; this was half asses at best.

I didn't have the 1/8 NTP fitting that was required to screw into the crankcase, So I used one of those rubber capped fitting that you push into the hole to seal, I didn't get to do a thorougher test but I know I do have oil pressure at idle and above it, will have to comeback to it and do it properly.

I rechecked the oil level sensor and I think it is the cause for my oil light staying on, plan on doing an oil change at some point; I might get lucky and it will fix itself, or I could pull the oil pan....

I Also Ended up fiddling with the TPS again, set it by voltage this time to 5.20V at idle(engine off), which became 5.22 after a quick test ride. was working good till it got hot then wouldn't take quick blips of throttle; would die and go back to idle. Gonna set it to 5V this time see how it goes. would be nice to get a colour tune to see how much this effects the idle mixture. Another thing to note; is is their an impact for having the engine running when doing this. Just gonna keep playing with it till, it works good.

The Fuel return relief valve also got some love, it was leaking which was annoying when removing the tank, pulled it a part polished it and replaced the O-ring problem solved.

Hi, the relay for the low oil indicator is under the seat, next to the tool box under the rear cowling. ( at least on carb Models) It is controlled by a float in the oil pan, the cable connects to the rear of the oil pan. That relay stays on if your oil level is low for a short pulse. The oil pressure switch is real time, info on current oil pressure. The relay tells you that you had a momentary drop of level in the oil pan. I had a scare when I started my -82 after full engine job. First running Ok, second start, oil light stayed on... I have disconnected the relay, oil pressure switch is enough for me.

Update.

Pulled the oil sump; float was stuck due to sludge buildup, this is resolved now. Internals looked good and gasket came off cleanly.

With the sump back on and not leaking, I started the bike up with high hopes of having the oil light going off when running. Well the oil light was still on, So I checked the electrical's and had the oil level sensor going to the input for the oil pressure and visa versa . With that sorted The light works correctly, which is good.

My Colour tune arrived as well, so I installed that to see how the bike was burning. Was a nice blue but the plugs were black all over with white at the ground strap. I have found with the colour tunes to get a decent mix, you should adjust till the colour is yellow and back off till it just goes back to being blue. So in doing that I ended up being back at the original scribe marks on the TPS.

With this all done the only thing to do it potentially change the throttle cables out for new ones, which have been ordered, and to sort out the front and rear brakes. The PO sealed the rear MC even thought the diaphragm was deteriorated, and the front MC piston isn't fully returning, so more to come.