Dennis, just for comparison, here are the records from Maxton.
I don't know what the bike was (might be a full 250, C15 BSA perhaps) and I'm not sure what the altitude is at Maxton. I'm sure the Cub would run faster given better conditions than at the salt flats.
These speeds are only one way though and are recorded at the end of the Standing mile.
250 CC Pushrod Records
9289 M/PG-250/4 PAUL HAVIR Paul Havir Oct-05 84.127
9289 M/PF-250/4 PAUL HAVIR Paul Havir Oct-05 88.440
9289 MPS/PG-250/4 P. D. H. Services Paul Havir Oct-06 91.491
9289 MPS/PF-250/4 P. D. H. Services Paul Havir Oct-07 84.717
Sam.