Lightweight Update

We still haven’t got the Lightweight running properly yet, though it is much improved.  The engine starts easily and now runs smoothly at idle at all speeds, and pulls pretty well – we can now get 60mph out of it – but still misfires on the over-run and at steady high rpm.

The fuel system certainly had some issues – the lift pump diaphragm was perished, resulting not only in poor fuel delivery but also in fuel contamination of the sump oil.  The stand pipes in the fuel tanks were clogged, further straining the delivery system.  I also suspect a small air leak from the cork gasket in the tank selector valve as the new lift pump has a small amount of air bubbling when hand priming, though there doesn’t seem to be any when the engine is operating the pump.  The new pattern carburettor was replaced with the stripped and rebuilt original.

The fault seems most likely to be in the ignition, and following the replacement of the coil, spark plugs and condenser, the distributor itself is the prime suspect.  It has been stripped for a second time, this time to check the cap for signs of tracking (it’s fine), to check the flyweight advance mechanism for the play on the cam shaft (the springs are good, but their fixed posts had been bent inwards creating some slack) and the points which don’t look too healthy.  A new set has been ordered and I hope they will cure the fault while allowing us to retain the original screened ignition system (partly for cost’s sake, but mainly to preserve the vehicle’s originality).  I’m mildly optimistic that we have found the main culprit; a bad set of points often produces ignition problems when the system is under high load with high engine rpm and weaker mixtures – exactly the circumstances we have.

Unfortunately, fitting new master and slave cylinders to the clutch haven’t cured the dragging clutch issue which results in 1st and 2nd gears crunching on the down-shifts and selecting reverse.  A new flexible hose is on order, but if that doesn’t cure it, the fault is likely to be with the clutch pressure or friction plates, which is no small job to rectify.