Have you tried cranking the engine with the ignition off to see if the draggy start is ignition-related or the fault of bad starter performance, engine friction, etc.? If it cranks at a normal speed with the ignition off, you've got an ignition timing problem. Otherwise, look for inadequate size battery cables, poor connections (especially grounds), or a low battery. A 6 Volt system should crank at a voltage of at least 4.5V, measured at the battery posts, or a 12V system should be above 9.5 volts, assuming you've got a fully charged battery. The cranking voltage should stay at or above those numbers for a minimum of 15 seconds of continuous cranking if the battery reserve capacity is good. Don't do the extended cranking test more than once every 20 minutes or so, to avoid overheating the starter windings.
Jerry
