On the let it rip window, press A, then when the ripcord is most closest to the launcher,
hold A, a bar will appear, try to get that bar the fullest you can and your RPM will rise.
Also, when you lvl up or your str increases, you will get more RPM

Use Cheat Codes >.> Or What He Said, Also If You Use A Rom I Suggest CheatEngine And
Memory Edit Your RPM Lets Say Your RPM Is 800 Pause Game On And Type The RPM You See In
The Memory Editor Like 800 Press First Scan Then Unpause Game Let It Run RPM Go Down A
Little, Then Pause Say Its 724 RPM Just Type That In And Press Next Scan And Keep
Repeating That Till You Get 1 To 8 Different Adresses Then Put The Adresses On The List
Below And Use CTRL Hold It And Click Lets Say 2 Adresses Right Click Go Into Value And
Edit It To 9999 RPM And Press The Boxes On The Left Under Catagory Frozen Now You Will
Never Be Beaten.

Enjoy

Use an engine gear and press the A and B buttons together to activate it.