If they run off coil ignition, then the fault lies in the alternator. These are accurately set and need specialist work. If they run off a dynamo, check to ensure the cutout box is working correctly.
The lighting is very poor. At normal running speeds, with the lights on, the ammeter registers a 2-amp discharge and after 30 miles the lights have failed completely?
The Miller voltage-regulator cartridge is at fault. Under normal circumstances the load should more than balance at average road speeds. There is no point in changing to the equivalent Lucas lighting set, because both the miller and Lucas sets have a normal output of 60 watts.
There is excessive noise coming from the engine. It seems to be coming from the timing gear?
Check the cam wheels. If there is clearance between the teeth, this is due to wear and they must be replaced. Other checks to be made are, the condition and concentricity of the cam bushes, and the state of the tappets and valve gear. Valve gear must be replaced as sets, as a worn pinion will rapidly wear out a new one.
There is excessive oil consumption?
The normal escape route for the oil is either down the valve guides, or up the cylinder bores. If it isn’t dripping out of the cases, check all these areas.
It starts ok when cold, but will not re-start when hot. When it has cooled, it starts?
The problem is the magneto fading out as it warms up. This is common and is often caused by old age. Other possibilities are over-tight valve clearances or the fuel supply is failing, due to the lack of float vent.
Experiencing handling problems mostly on cornering?
If the wheelbase is not 52”, then incorrect setting, or wear of the top fork links is the most likely cause.
Not getting a charge from the dynamo?
Check all connections are made good. Make sure there is a good earth connection to the field coil. The wire is attached to the housing but is not earthed on it’s own and relies on a good connection to the engine. This earthing is compromised by plate 1/43-dynamo packing washer, which looks like a big fibre washer, which sets the housing off the engine and insulates the dynamo.
The engine rattles at 30mph and above?
If either the engine pulling or running light does not affect the rattle, the timing gear is suspect. Examine both cam levers that operate the cams for wear. If the rattle stops when the engine is pulling, then there is movement in the big-end assembly.
Wear on the gearbox main-shaft is a problem?
Check the truth of the bore and sleeve gear. If un-true, have the main-shaft ground back to the true diameter, then hard chromed, before grinding back to sleeve gear bore size. Make sure on assembly, it is all well oiled.
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