I need to know how many ML of oil I need to put into 5L of petrol for my Kawasaki kx80 1995 or 1998 model and its not a automatic mixer I have to mix the fuel manually

50 to 1
50 fuel to 1 oil
one litre capacity on your unit
1000 mL is a litre
so 20 mL oil per 1000 mL Fuel

see
https://www.manualslib.com/manual/1204894/Kawasaki-Kbl23a.html?page=11
for confirmation

check witha dealer because at that year it should have an oil metering pump which mixes the oil correctlry to suit all rpms
There should be a separate oil tank for the oil

try this link might help you out.
http://www.haniel.co.uk/fuelmixcalc.html
or this one.
How many ml to make up 5lt at 1 25 mix Google Search

Milliliters to Gallons conversion Visit this site to get converted.
https://electronicshelponline.blogspot.com/

2 stroke hand tools are generally 50:1
100ml of oil in 5L of petrol

older Vespas without separate Oil-tanks need a premix of 1:50 oil in the gasoline - but yours is an automatic oil-mixer type.
check the oil-level-glass under the seat near the choke.
it must be full of oil - the oil tank can hold about 1 liter of 2-stroke oil. How much oil did you fill in?
Probably the previous owner removed the oil supply tube and filled always an oil-gasoline premix. You better ask him about it. If the tube was removed then there was no oil supplied to your engine and it got stuck and the engine bearings are blown.

how many cm3 engine?
normal - min 90 ml for 5L gas but normal 110 ml oil for 5 L gas, best for engine is 130 ml oil for 5 L gas.

is the compression good on your engine have you checked and cleaned the carb out also are you running the right pre mix ratio about 32:1 which is about 156 ml oil to 5 litres of petrol

Like most 2 stroke weedwackers they run on a 25:1 fuel ratio. It is advised that you mix the petrol & oil in a separate container (remember to shake it for a few seconds) first to ensure it mixes properly.
Example: 1 Liter of petrol needs 25ml of oil. (Use 2 stroke oil) Hope this helps.

Yes if you have a 2 stroke. You will need to look at the manual, or somewhere on the bike for the ratio.