If the brake fluid level in a motorcycle decreases over time, even without any visible leaks, it could be due to a couple of factors:
Normal Wear and Tear: As the brake pads wear down over time, the brake calipers need to extend further to maintain proper contact with the rotor. This extended movement requires more brake fluid to fill the additional space created. Consequently, the brake fluid level can gradually drop as the brake pads wear out. This is a normal process, and it indicates that it may be time for a brake pad replacement.
Brake Caliper Piston Seals: The brake caliper pistons are responsible for pushing the brake pads against the rotor when you apply the brakes. Over time, the piston seals can wear out or become damaged, allowing a small amount of brake fluid to bypass the seals and accumulate inside the caliper. This internal leakage may not be visible externally but can result in a gradual decrease in the brake fluid level.
It's important to note that brake fluid should never decrease significantly without any apparent cause. If you notice a substantial reduction in brake fluid level or suspect any brake-related issues, it's crucial to have your motorcycle inspected by a qualified mechanic. They can diagnose the problem and ensure the braking system is functioning safely and effectively. Regular maintenance and periodic checks of the brake fluid level are recommended to catch any potential issues early on and maintain optimal braking performance.