I'm thinking these were not Estes model rocket motors. As a kid we glued those to everything with wheels. Unless it was super light the motors would not make a big impact.
And for our bikes - trying to get two "D" big engines to ignite at the same time was really hard to do. 
But when we finally got the ignition thing down we were able to ride past the girls and light them up - it wouldnt make us go much faster but for 5 seconds it made a great sound and a bunch of smoke!
Ah, cool. Yep, those rocket engines went quick. Sure went quick! PFFFFT! ALMOST makes me want to fool with them again but I know it’d be frowned upon by the sour-ass city cops here. Too noisy. Sure were fun, though!