Thanks Greg,
I have just found this here https://www.motorcyc...y-mann-machine/ it seems that Dick Mann's bike was the only one prepared by American Honda. The other 3 factory bikes, for Ralph Bryan, Tommy Robb and Bill Smith, were prepared by Honda Japan and there were differences between them. Hansen also seems had a "difference of opinion" with Nakamura during the end of the race and he was sacked by Honda shortly after. This makes sense as to is why Honda weren't pleased.
Why it set back Honda's reputation in North America after that though I am not sure. They certainly didn't appear as an official team at Daytona or the AMA road racing series after that until it went to superbike regs. In Don Emde's Daytona book he says they elected not to enter in 1971. Gary Fisher's CB750 entry in 1971 was a privateer effort, I think tuned by Pops Yoshimura, and he did lead early on. I can see in 72 there were entries for George Kerker and in 73 for Morio Sumiyama, Steve McLaughlin and George Kerker, were these also Yoshimura entries? So was Honda's withdrawal connected to the 1970 incident? Or was it because they thought the 2 strokes were too fast, but 4 strokes still raced and won for a couple more years at Daytona and other AMA road races.