I just took the spring off the rear plate and went to the hardware store and found one that was similar in size and alot softer and both of ours work great now.
Tekno RC, Alpha Plus Engines
AKA Products, Lutz RC, A-Main Hobbies
NitroPro Fuel, Hot Headz Engine Heaters
Raceform Bodies.....Reilly Paint (Just Plain Wicked)