Before reassembling the engine, I measured each of the shims and shimmed surfaces for reference. Shimming is an important part of blueprinting the engine, but it isn’t a very well-documented area. While I still don’t have any info in this area, I am starting to compile the parts necessary to do it right. Shimming seems to fall into that “30 years of experience” category. Making the gearbox shift incredibly smoothly can be done by perfect alignment of each gear with tiny shim stock. Crank end float needs to be perfectly tuned by adding and removing shims between the crank and main bearings. How this is done or measured? I have absolutely no idea…yet.

UPDATE : I have compiled a list of shims from McMaster-Carr for rebuilding the 650.

Larger gear assembly (25mm / 17mm shafts)

• 33.65mm OD
• 25.41mm ID
• 2.75mm thickness

• 32.35mm OD
• 25.21mm ID
• 0.50mm thickness

• 25.01mm OD
• 17.19mm ID
• 4.00mm thickness

• 25.01mm OD
• 17.19mm ID
• 0.25mm thickness

Smaller gear assembly (25mm / 20mm shafts)

• 32.37mm OD
• 25.22mm ID
• 1.00mm thickness

• 32.37mm OD
• 25.22mm ID
• 0.50mm thickness

• 26.81mm OD
• 20.25mm ID
• 3.00mm thickness

Gear selector assembly (45mm / 40mm shafts)

• 48.65mm OD
• 45.25mm ID
• 1.00mm thickness

• 45.66mm OD
• 40.28mm ID
• 1.00mm thickness

• 45.66mm OD
• 40.28mm ID
• 0.20mm thickness

Crank (35mm shaft)

• 47.85mm OD
• 36.49mm ID
• 0.50mm thickness

• 47.85mm OD
• 36.49mm ID
• 0.20mm thickness

Miscellaneous

• 24.87mm OD
• 19.65mm ID
• 1.00mm thickness

• 27.85mm OD
• 25.21mm ID
• 0.50mm thickness