The many things that were put into the engine to Maximize power output and efficiency also have the benefit of making the TRX 2.5 Racing Engine easier to tune. It's tolerant to to a very wide range of needle settings and variations in temperature, altitude, etc. The engine is tightly sealed with o-rings throughout to eliminate air leaks that can cause inconsistent running performance. The engine responds precisely to changes in the needle settings for easy, predictable tuning. Engine is supplied with Pullstarter that can easily be removed for use with the EZ Start2. Engine is backed by the Traxxas Lifetime Engine Replacement Plan. Included in package: Complete engine with recoil starter and air cleaner installed Air filter oil Installed glow plug (3232X) Break-in instructions and owners manual Engine tuning DVD Decals and warranty card Requires use of Traxxas exhaust manifold."