Get a 4age.... Jist kidding.
If it runs well on start up but dies when warm it might be too rich or over fueling.
Vacuum advance on your dizzy could be out too so when it curves back down to idle speed with excess petrol bogging it down plus your timming being out will cause it to cut out.
Try setting your timming right and bump up your idle to keep it alive, you'll probably need to get the Webber tuned with a new needle jetted to suit the motor to get the most out of it.