the smaller black cog is the 2nd gear, theres a clutch in there that engages when it hits a certain rpm.

As for the fuel line, just turn the tank the other way around, thats what most people do to counter the fuel line problem. you might need longer fuel lines though.

Theres a thread here that discusses rs4's problems and other chat. Just have a read
[link]http://www.rcuniverse.com/forum/m_5416029/mpage_1/key_/tm.htm[/link]