If your classic is reluctant to start, here are some top tips on how to get it going. Get an assistant to pull the choke out. Look underneath the carburettors and check that the main jet holders are being pulled down by the choke mechanism. Investigate if they aren’t. Disconnect the fuel hose to the carburettors and place it in a petrol can. Turn on the ignition. You should hear the electric pump clicking and there should be a strong flow of fuel. If it has an SU pump, they are prone to burning their internal contacts, causing erratic operation. The contacts can be cleaned with fine abrasive paper. If the contacts are badly burned, replace the pump. If the fuel appears to be very aerated, check that all pipe connections are sound and tight, and the rubber hoses are not hardened, damaged or porous. Replace any ageing ‘disposable’ fuel filters and clean any others (usually wire meshes in the tank pickup, fuel pump and/or carburettor).
Next, move on to the ignition. Replace the points and set the gap. Set the ignition timing so that a test light connected between the terminal on the distributor and earth just lights as the timing mark on the pulley meets the static timing mark on the timing case displayed in your workshop manual. Turn the engine by hand. Replace the condenser with a new one or – preferably – one that you know is good.
Ensure the wire from the distributor goes to the coil terminal marked ‘CB’ and that it’s undamaged and tightly attached. Check the wire that runs from the ‘SW’ terminal back to the ignition switch.
Clean the distributor cap, rotor arm and the top of the coil with a petrol-wetted rag and inspect them for cracks and burning. Make sure the metal contacts of the cap are not burned or corroded and check that there’s a sprung carbon contact on the inside. Clean and inspect the HT leads.
To test the rotor arm, remove the king lead and hold it 5mm from the engine block using insulated pliers. As the engine is cranked, a strong spark should jump from the end of the lead. Now reconnect it and remove a spark plug lead. Push a bolt inside the plug cap and hold it 5mm from the block. The spark should be just as strong as before (though not as frequent).
Clean or replace the spark plugs, setting the gap as detailed in your workshop manual. If the problems persist, check that the valve clearances are correct. If the clearances are too small or non-existent, vital compression will be lost and the engine won’t start.