Sandcast and Diecast Cases

There were two types of cases used on the 1972 models, the earlier was a sandcast from eng # 750 001 to 750 401.  There is some dispute as to the final number used of the sandcast engines. From eng # 750 402 on they were of diecast manufacture from personal experience, happy to stand corrected if images of cases from #750 403 to #750 405 show them to be sandcast.

The sandcast cases were heavier and arguably stronger than the later diecast. However both types have been used successfully by racers the world over with power output up to 100hp. The area around the main bearing sleeve is much thicker on the sandcast case.

For your interest here are a number of images showing the internal and external differences in appearance between the two. To date, these images and the detailed differences have not been illustrated by any author.
The sandcast example will be to the leftside and the diecast to the right.

Outer Case Halves

The detail shots illustrating some of the differences are below.

Inner Case Halves

The detail shots of some of the differences are below.

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