[Mr.Fixit]

Pull out plug #1, rotate motor unto "puff" of air comes out of spark plug hole. This is the TDC that firing occurs on, not the other TDC. Timing mark should be at TDC now, if not rotate back a little bit until it is. Pull off dist cap and make sure it is pointing at lug #1. Make sure the firing order is correct it may be 13726548 or 15426378. Make sure the intake valves are actually closing, setting valves "dry" is difficult and it's all too easy to overtighten them so that they hang open a TINY BIT when they should be closed. I had that problem on my very first motor, everybody kept saying "You're 180 degrees out" but I wasn't. Figured it out by bringing #1 to TDC and putting a leak down tester on it, the air came rushing back through the carb. Rotating it over either direction didn't make the valve close, so I readjusted all of them, going easy on the preload, and it fired off nicely. If you have a really wild cam, this can happen every time you start it when cold if you don't do the following: depress pedal to floor all the way once and release, keep foot off pedal, crank motor and it will fire off, then you may touch the gas pedal again to keep it running.