I2C1_WriteByte(MPU6500_ADDR, 0x6B, 0x00);

Per datasheet, first step is to "Make Sure Accel is running". Sleep is by default.

In PWR_MGMT_1 (0x6B) make CYCLE =0, SLEEP = 0 and STANDBY = 0

In PWR_MGMT_2 (0x6C) set DIS_XA, DIS_YA, DIS_ZA = 0 and DIS_XG, DIS_YG, DIS_ZG = 1