The amount of fluid that will leak out from the primary case of an M8 Harley when you open the derby cover while the motorcycle is on a jiffy stand can vary. However, it's important to note that the primary case typically contains the primary chaincase lubricant, also known as primary fluid or primary chaincase oil.
If you open the derby cover while the motorcycle is on a jiffy stand, some of the primary fluid may leak out. The amount of leakage can depend on various factors such as the specific model of the M8 Harley, the oil level in the primary case, and the angle at which the motorcycle is resting on the jiffy stand.
To avoid excessive fluid loss, it's generally recommended to ensure that the motorcycle is on a level surface and upright when opening the derby cover. This helps minimize the potential for fluid leakage. Additionally, it's a good practice to check the fluid level in the primary case before performing any maintenance to ensure it is at the proper level.
For accurate information regarding your specific motorcycle model, it's always best to consult the owner's manual or contact an authorized Harley-Davidson dealership or service center. They will have the most accurate and up-to-date information for your particular bike.