You will especially notice them get weak if you use traxass s#!tt fuel! My Lhs ran out of fuel and only had traxxas 33% and I bought some, tried to run a tank through but stalled and broke my pullstart trying to get it going again. Then went through 3 glow plugs on the next two tanks! Never again, that is total crap, I dont know how they can sell it.[:'(]