Just check all your wiring again......took me 2 days farting around and my 70 year old next door neighbour 2 seconds to fix me up
Is your 12V ignition wire going to the amp directly from the ignition circuit? ie: not your accessories? eg: if you tap a wire off your cigarette lighter, that circuit gets disabled when you turn the key to start. Spark checks great when accessories on, but turn the key and nothing.
Check all your connections for dodgy crimps etc.
Also, if you've tapped off some other accessories line you may have a blown fuse n the fuse box.
Do you have your dizzy in correctly? ie: not 180* out firing on the exhaust stroke?