Distributors can develop a whole raft of problems , mostly due to wear and tear , but some were designed in .
The first and very obvious one is when the mounting flange is chewed to death around the slots , or the ends of the slots have been cut open by people who have got the cam timing wrong and then cannot get the ignition timing right ( see the " Bedside Book " on cam timing ) .
If the body is otherwise OK it may be reclaimed by turning the flange off and screw cutting 37 mm diameter x 1.25 mm pitch . A new flange can be made up in "Dural" and then screwed and Loctite'd on , being careful to align the slots correctly . A 1.0mm deep by 1.5mm wide groove for an "O" ring should be turned round the locating spigot .
Upon dismantling it may be found that the aluminium carrier for the contact breaker is broken in two , Stewarts may be about to re-manufacture these parts so try them first . If all else fails put in a few extra screws to clamp the broken parts firmly into place .
It also may be found that the hardened steel thrust washer between the oil seal and the driving dog is missing , this MUST be replaced on reassembly .
On the distributor shaft , the carrier plate for the auto advance system tends to come loose and should be bronze welded after clamping into place , it is a good idea to do this even if it is not obviously loose .
Part way up the smaller shaft is a neck down and a small oil hole which promotes fatigue , eventually causeing the shaft to break off , so while you have the torch going fill the neck down up with bronze weld , afterwards turning or filing the shaft back to size and to checking that it still runs true .
At the top of the smaller shaft the two small driving dogs for the rotor carrier may be damaged or missing , build up with steel weld and recut , or you can replace the whole of the smaller shaft with a solid one pressed into the larger , being careful to get the rotor properly aligned .
The pivot pins for the bob weights are too short , so as wear developes the off centre pull of the springs causes the weights to rise up from the plate , eventually to the point where they hit the bottom of the contact breaker mounting . This creates noise and further wear , it also probably plays Hell with the ignition timing .
The original pins may be removed by careful drilling from the bottom of the plate , then a new pair of pins plus sleeves for the weights should be turned up as shown below .
You could try riveting the new pins into place but they are easily damaged , in the three distributors I have reconditioned the pins were brazed ( Silver Soldered ) into place . Care must be taken to ensure that the braze penetrates fully round the shoulder and right through the plate , ( a properly done brazed joint is a thing of beauty ) . The weights should be drilled and reamed 6.0 mm and the sleeves pressed in .
Not only do the weights now have much larger bearings , but also the pull of the springs lies within the bearing length so there is no tendency to lift the weights up.
Finally if you stll have an origonal capacitor put it in a museum and purchase the modern replacement that Stewarts now sell ( from a Honda I believe ).
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IGNITION COILS
Having done all of the above you can still be in trouble with ignition , my first S-8 was an absolute Bitch to start and ran as flat as warm beer despite everything about it being new or reconditioned and converted to 12 Volts . Finally after a bit of trial and error I threw out the small brand new motorcycle coil and replaced it with a Lucas DLB-101 Supercoil as fitted to Land Rovers and Mini Coopers ( seemed a good enough pedigree to me ) . This coil was physically so large that it was fitted between the frame rails on top of the electrical boxes , being out in the fresh air is no bad thing because coils do not like running hot .
The bike was instantly transformed into an easy starting , reliable one that was a joy to own , quite quick too for a Sunbeam as it would easily do 80 with throttle to spare .
This is not the first time I have had this trouble with motor cycle coils and cured it the same way , so if your Beam won't start look to the coil .
FINDING TOP DEAD CENTRE
There are various ways to find way top dead centre when setting up an engine , the method I have always used involves the body of one of the old detachable spark plugs and a piece of soap . Firstly you get the engine close to t-d-c on the compression stroke using a piece of wire through the plug hole , then fit the plug body . If a soap bubble is now drawn across the plug body opening , any movement of the piston is magnified many times over by the movement of light on the soap film . Using this method it is quite easy to set t-d-c to within one degree and is especially useful when dealing with side-valve engines .
I read about this when I first started motor cycling about 40 years ago but I have never met anyone else who has heard of it .
