Once you can play the scale in this manner without losing the rhythm, try memorizing the rhythm on one note first, and then improvising with it. Play any notes from the scale in any order you like, but be sure to keep the rhythm exactly the same every measure. The following example demonstrates four measures of an improvised melody using this set rhythm.
The next step is to move the quarter note to the second beat and play eighth notes in the rest of the measure. Once again, memorize the rhythm and then improvise with it. Then repeat the process with the quarter note on the third beat of the measure, and then again on the fourth beat of the measure. Each of these rhythms is shown on one note in the example below, along with the previous rhythm.
It is also worth learning to improvise with a constant stream of eighth notes. This is difficult at first, because you get no time to think ahead between any of the notes. However, if you work at it you will find that it gives you more control over your improvising in general. The following example demonstrates four measures of improvisation using constant eighth notes.