Pull StartMuch like the pull start mechanism on a lawnmower, a pull cord is attached to the nitro engine and you pull the T-handle attached to the starter cord assembly to spin the flywheel and start the engine.
Also called a recoil starter, the pull start mechanism causes the engine to sit slightly higher, affecting the center of gravity -- a possible concern in RC racing.
These videos demonstrate the pull-start method for a nitro RC:
Bump Start (Starter Box)RCs without a pull start system have an opening in the chassis that provides access to the flywheel. The RC is placed on top of a starter box that has an electric-powered spinning rubber disk sticking out of it that makes contact with the vehicle's flywheel and rotates it to start the engine. This is known as a bump start system because the flywheel is bumped against the disk in the starter box to get the engine started.
There may be a slight weight advantage (lighter) for a non-pull start engine because it doesn't have the extra weight of the pull start mechanism. However, with the non-pull start engine you'll need to carry around the starter box and have access to a power source for the box.
Electric StartShaft starter. In place of the pull start mechanism, a shaft starter electric start RC has a special gearbox into which a shaft on the end of a small handheld electric motor (much like a cordless drill or rotary tool) is inserted. With the push of a button it spins the engine to get it started. Some nitro RCs come equipped with an electric start system while other RC models can be retrofitted with one. The Losi Spin Start Handheld Starter and the HPI Roto Start Electric Start System are examples of this shaft starter type of electric starter.
On-board starter. An on-board style of electric starter, such as the Traxxas EZ-Start, places the small motor for the electric start system on the RC then uses a battery-powered handheld tool to power it and to automatically ignite the glow plug at the same time.
Some nitro models with an electric start system may also be configured to work with a starter box to provide an alternate starting method. When using the alternate bump start, the automatic glow plug igniter (if eqipped) can't be used so you'll also need a glow starter.
As with the bump start method, having a non-pull start engine means carrying extra equipment -- the electric starter as well as its batteries and charger. The on-board componenents of an electric start system also add a little bit of extra weight -- a concern primarily in serious RC racing.
Traxxas provides several Engine FAQs that cover their EZ-Start system including how to install the EZ-Start system and which engines will support it.
These videos demonstrate the electric starter method for a nitro RC: