My magnum starts just fine and idles until I hit the gas, then it starts to go from full throttle to the brakes locking up. I am guessing it is a radio issue since the fail safe would put the brakes on. Any suggestions anyone?

bypass the failsafe and see what if it still does it.

The NX doesn't have a failsafe, I know, I've watched mine run away at full throttle a few times before I purchased a Duratrax failsafe, works great. As far as the twitching goes, make sure you're holding the radio straight up and down and not parallel to the ground.

swap the servos around on the reciever. see if its the servo or the reciever that is the problem and replace the dodgy item mate. cen radios are notoriously poor - i expect it to be the reciever, its normally the prob anyway.

I added a failsafe, Venom failsafe with temp and radio. I bypassed the failsafe and it still does it. I think the receiver might be bad or the servo. I dont know what else to try. All batteries are good also.

The motor is not stock either, not that it matters.

Any other suggestions?

swap the servos around on the reciever. see if its the servo or the reciever that is the problem and replace the dodgy item mate.

First off thank you all for your help and suggestions!

I tried the servo switching when I bypassed the failsafe, it did not work. I am just going to buy a better radio and go from there. I am pretty sure it is the receiver and did not really like the radio anyway.

I bought the engine conversion kit for it anyway and will be putting in a .21 in it so I will just the whole overhaul then.

Thanks again