A question for the sand cast gurus

[H2Eric]

According to John Wyatt's book 'Original Honda CB750' the first 7414 engines were made by the gravity die cast process or sand cast if you prefer and then the pressure die cast process was used. The question is, at what date did the change take place?

[AshimotoK0]

I think around September 1969 Eric  Not that I am a sandcast guru.

[H2Eric]

Thanks Ash
What I'm trying to figure out is what crankcases were used on the racing bikes at the Daytona 200 race in March 1970. Originally these bikes had crankcases made of magnesium, but due to unexpected expansion problems and the crank tending to bind, the cases were changed with new alloy ones that were flown in from the factory in Japan. Therefore, if the method of production changed in September 1969 its logical that those crankcases were made by the pressure die cast method and not the earlier sand cast process. I've been told that the original magnesium cases were smashed in order to recover the pin that holds the kick start shaft in place and hence the drive for the oil pump. One set of magnesium cases apparently burned rather well after Ralph Bryans crashed in practice.