need help with converting a hyper 7

[BrianG]

4s on a 5000kv motor geared 46/9 will be running ~55mph. Way too fast for such a high kv. I can almost guarantee you are gonna have heat issues. With that high of a kv, I would go no higher than ~25mph, which is a 5T pinion (not available). You can run that motor, just don't expect it to last long, and your batteries and ESC are also going to be stressed.