ref carb 1 

body marked Nissin 13f2  5/8 also i notice N7 near bar clamp may have a few marks from storage 

The Nissin 13F2 master cylinder is a motorcycle brake master cylinder that typically features a 1/2" (12.7mm) piston and an integrated fluid reservoir. It is an OEM (Original Equipment Manufacturer) part used on a variety of motorcycles from different brands. 
Key characteristics
  • Piston size: 12.7mm or 1/2". This is a key specification for matching the master cylinder to the correct brake caliper setup.
  • Integrated reservoir: Features an integrated brake fluid reservoir, rather than a separate unit, making it a compact, all-in-one unit.
  • Axial design: The piston and lever act along the same axis as the handlebar, which is a standard design.
  • OEM Part: It is frequently found as original equipment on numerous older and mid-range motorcycles from brands like Honda, Suzuki, Kawasaki, and Triumph. 
Applications and compatibility
The Nissin 13F2 master cylinder is an original fitment on a wide variety of motorcycles.
  • OEM replacement: If the original master cylinder on your bike is a 13F2, you can replace it with an identical OEM or high-quality aftermarket unit.
  • Retrofit: Due to its common 1/2" piston size, it can be used to replace other similar OEM master cylinders. However, check compatibility with your bike's original brake hose before installation.