Shim stock for front motor mounts

[dommi7]

I just ran across a galvanic corrosion design guide at work today. According to the table, in a harsh environment, there should not be more than 0.15 V difference in the anodic index for dissimilar materials.
Cast aluminum containing Silicon is rated at 0.90V, non-Si cast Al 0.95V while carbon and low alloy steels are 0.85V. So even in a high humidity and salt environment, there should be little to no galvanic corrosion between the motor case and frame. Shims, if used, should be steel.
(As we could have surmised, as these bikes have been on the road for 70 years already without adverse effect)

I agree dissimilar metals can have a galvanic reaction and have experienced it within the electrical industry. However, I wondered with steel frames and sand cast aluminum cases, did the MoCo treat or coat hardware/shims/frames/cases to prevent a galvanic reaction? My concern coating parts is the potential reduction or elimination of ground continuity which is needed for circuit breakers, etc. Just my 2 cents and wondered what others have experienced.

[billpedalino]

In over 40 years, I've never used shims under the front motor mounts and have never broken a front case casting. Also, the gavanic potential between 304-320-type stainless steel (like a feeler gauge) and aluminum is very low. If you coose to shim, I wouldnt worry at all about corrosion between these two metals.