the timing needs advancing, slacken the distributor retaining nut so you can rotate the distributor to advance the timing. 1st start the engine and let it warm up when the choke is fully off, slacken the nut so you can rotate the distributor, turn up the tickover and move the dizzy to find a spot at which it is running the fastest, nip the nut back up and turn the tickover back down to a steady burble. rotating the dizzy the wrong way or too far you will hear it start to splutter or falter so youre looking for that optimum sweet spot. once set rev the engine to make sure there is no flatspot as it goes through the rev range, do this with a gradual rev increase and by a series of throttle blips and listen as it goes up and settles back down for any faltering, if it responds well and is smooth throughout you have sorted it, over the next weeks monitor the sparkplugs to look for signs of hot or weak running just to check you don't have it out or have a mixture problem
