You can check the motor oil or the transmission fluid.
Most motorcyles have a liguid clutch which means they run in motor oil so when you change your motor oil you are changing your (gearbox) transmission oil and to check your (gearbox) transmission oil level you check the motor oil level.
Via the dipstick
When you change the oil in a 173cc motor you will need to refill it with 25 to 28 ounces of oil. You should be sure to check the oil with the dipstick to ensure that it is at the correct level.
To check most transmissions on Honda motor cycles you check engine oil. They have a liquid clutch that are in the crank case oil.
If it's new vehicle. Then check owners manual. If it's a used vehicle 10w30 or 10w40 Castrol Motor Oil
How to Change Your Motor Oil check related link below...
4 qts of motor oil then check and add only if needed.
no no no put oil in and hope the motor is ok. check the oil every time you fill up
1 quart usually. Check the DIP STICK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
in the front of your motor there is a yellow handle,pull it up that is your oil dip stick
you can check oil grades on www. castrol. com