When I try to start my John Deere 180 lawn tractor I get a machine gunning rat-tat-tat sound and it doesn't start. Can anybody tell me what my problem is?

How old is it? Are you sure you got oil and gas in it? You may have to have someone (or yourself) to look inside for any problems as there are many possibilities for the problem.

Hi,
If this is the 20 yr old 180 with the FC540V 17 HP Kawasaki, it is probably the ignition/igniter. Some have the two piece and some have a one piece. If it is two piece, it is better to replace the coil with the newer one piece unit since in the two piece setup one piece usually fails the other.
The coil is of course under the blower housing on top. The trigger, if equipped, is a 1"x1 1/2" silver rectangle behind and beside the dipstick.
It has white wires attached.
Peace,
Clarke