Did you set the timing "statically"? If you have, ignore the following.
Turn the engine until the #1 cylinder is on the compression stroke. You can find this by checking the valves or by pulling a plug and putting your finger over the plug hole while you (or someone else) moves the crank back and forth near TDC/UDC (rotate the harmonic balancer or the flywheel). Once I find this, I line up the pointer on the clutch-housing to the ball/mark (bb?) in the flywheel.
Then, make sure that the #1 ignition wire is where the rotor is pointing. Check sequence: 1-5-3-6-2-4
