What is the correct oil I should use in a Honda APE100?

How did you confirm oil sensor is ok ? Personally I would change to be sure

you could but I strongly suggest that you use the correct oil as bikes need special oils for reliability.
all it takes is a call to a honda service dealer to get the correct information

Typically they use a 10w30 oil in the engine and a non-detergent SAE30 oil in the pump portion.

change oil it every 1,000 kms.

there is some room for adjustment, i think about 10 oz but the springs could be progressive and use different amount of oil...Call a honda dealer have them explain the difference including the reason for different weighs of oil, to help you set your suspension correct fo an air ride shock

First off you are using an incorrect weight oil in your Honda. Your Honda requires 5W20 and not 5W40 which is way too heavy. Change the oil and filter every 5,000 miles and use the correct weight and a quality filter such as Bosch, Purolator, or Wix.

Correct spark plug gap is 0.6 -0.7mm and oil viscosity is variable like SAE 20/30w some thing like this and also depends on weather conditions.

If you go to a reputable motor factor,
you can only be sold the correct filter for the civic.
As there are soo many variables in engine type, it's almost impossible to tell, oil volume, or which type filter.
However, I will say, be sure that you don't mix semi-synthetic oil, and mineral oil.
Oil changes should be undertaken every 30,000 miles, (unless under extra work load, (in which case, slightly more regularly))

Otherwise, 10/40 or 15/40 grade oil, is perfectly fine.
The trick to not overfilling the oil, is simply just to take your time, clean the dip stick and retry, until you have the correct reading.

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GN4 honda oil