Like druss says

Also you should change that tamiya battery connector to high power connectors like deans,trx if your soldering not the best just pop into a model shop they should sort it for a few quid

Surprised those motor to esc wires dont heat up i know when i had a gt3 motor it heated mine up alot even on nicad packs []

Looks a good setup though bet it flys!! love those gt motors i had a 13x4 it had tons of torque

[quoteIt's strange because it works fine till it get to about 40 yards away then it starts spluttering ][/quote]

Is it doing that striaght away on a fresh battery cos im sure the wires are struggling to cope with the amp draw.