What time was achieved on Saturday 29th August by the rider who recorded 25' 01.89 90.438mph on Friday 28th August?
create table table_23465864_4 (sat_29_aug varchar, fri_28_aug varchar, PRIMARY KEY (sat_29_aug))
select sat_29_aug from table_23465864_4 where fri_28_aug = "25' 01.89 90.438mph"