I would suggest to test the condenser first
Clean the contact points
Clean the contactor for the HT lead (look on the drawing all the spring, button, holder and there is a contact spot on the coil)
Make sure the spark plug end of the lead is in good shape, the contactor for the plug at that end of the lead should have a spike that goes into the conductor of the lead.
When you clean the bits use some contact cleaner OR some brake cleaner OR alcohol (running type not drinking) and a metal file. Using abrasive cloth can leave behind bits of grit that can be problematic. ALSO do not use carburetor cleaner because it has lube in it and the lube will prevent good contact onyour electrical components.