I just replaced my throttle servo on my HPI 5SC with a HiTec HS-5645MG. Once I got it hooked up I noticed it turns opposite of the stock servo. Throttle and brakes work backwards on the radio. I can turn the servo around 180 degrees to get it to work right, but then linkage is way off. Can someone tell me what's up?

I also replace the steering servo it works great.

99% of the radios out there have a channel reverse switch or programming option just for this reason. Reverse the throttle channel, re-center the servo and linkage and you'll be good to go.

Flip the throttle reversing switch on your transmitter. This happens sometimes when servos are replaced. It's an easy fix. The switch should be rather small, somewhere possibly on a flat panel section of your transmitter. There is one for the steering too, but since your steering works fine, no need to change that one.

Ok thanks guys...............Now I had installed a RC kill switch which was working. Now that I reversed the servo, when I loose connection it goes to full throttle instead of braking. Any ideas?

Ok I figured it out.........Had to reset the fail safe.