1952 Sunbeam S8 – Resurrection




Part Four of Four – A Motorcycle Emerges



Lifting a complete engine and gearbox, with the cylinder head and alternator already fitted, off the floor and straight into the frame, takes a bit of practice but I prefer to do it that way. I also lift them out the same way. I engage the rear (gearbox) mount first and then rest the engine onto the front engine mount before fastening both mounts. I leave both the engine and the gearbox dry until it is in the frame. What would be the point of lifting several litres of oil in addition to the already considerable weight of the lump?



When you work on bikes every day, there is a risk that one day you will start an engine with no oil in it. My strategy for avoiding that is two-fold. Firstly, I write on the engine case the words “No Oil” in black felt tip. Once oil has been added, I clean off the warning message. The second line of defence, before starting the engine for the first time, is to turn the engine over with the kick-start lever, with the oil pressure switch removed and the ignition turned off, until oil flows from the aperture. That confirms that oil is present, the pump is working and oil is just a second away from the important bearings when the engine starts. Remember that the bearings have already been lubricated during assembly.

On this occasion, however, oil didn't appear at the aperture, even after a minute of turning the engine over. This had never happened before. Numerous possibilities were considered. Some investigation eliminated the most obvious ones until I was left with the realisation that the only option left was to look for the cause in the oil pump itself. I drained the oil and dropped the sump pan and placed a tray under the engine. I filled a glass jar with oil and supported it under the scavenge pipe. I watched oil being drawn up from the jar, as I turned over the engine, and it immediately fell into the tray. It was spilling out from an opening in the oil pump body where there should be no opening.



For a reason unknown to me at the time, a “permanent” core-plug had been drilled out of the pump body and left open. A discussion with the current owner ensued. He said that the previous owner had experimented with re-routing the oil out from the pump, through a filter, or possibly a cooler, and back into the engine via the hole for the oil pressure switch. It was a flawed scheme that, fortunately, never reached fruition but its legacy was a sabotaged oil pump that needed to be restored to its proper function. Out came the engine again, the gearbox separated, the timing chest opened up and the rear main bearing carrier plate withdrawn, to get access to the pump. Plugging the unwanted hole and peening the plug firmly in place took no more than a few minutes. The whole incident took somewhat longer but the engine was back in its frame the same day, this time with a working oil pump. A small backward step but the project was now marching forward again.





Final assembly of the engine could proceed, starting with the oil pressure switch, carburettor, rear engine damper, distributor, clutch cable, exhaust system, Layrub coupling and drive-shaft.

The electrics box and the battery box were bolted together back-to-back and the electronic voltage rectifier/regulator fitted. A longer bolt was also provided to act as an anchor point for a common earth. I like earths. The standard Sunbeam wiring scheme doesn't make much provision for earths but relies on the frame, engine and cycle parts being electrically connected via various, more-or-less accidental points of contact. Miraculously, it seems to work most of the time but my preference is not to leave it to chance. Achieving good contact between parts that have been newly powder coated or painted requires more scraping and chipping than I feel comfortable with so I prefer to add dedicated earth wires to do the job.





With this bike, I had an opportunity to indulge this preference while making a new loom because the bike had, up to this point, no wiring at all, since the original loom was not included in the inventory. There are many prefabricated looms available ostensibly for a Sunbeam but I have never seen one that conformed fully to the original wiring scheme and actually fitted correctly. Beside which, they do not satisfy my fetish for reliable earths. My preference is to run an earth from the rear light cluster to the common earth in the electrics box, another from the gearbox to the common earth pillar and a third from the headlamp shell, either to the common earth pillar or to the front of the engine casing. The battery and the components in the electrics box also share the common earth.

The two boxes were bolted to the frame lugs. The stays for both mudguards, the mudguards themselves, the number plate bracket and rear light and the headlamp shell were all attached to the frame. When I am assembling a restored bike, I use new fasteners that are as close as possible to the original fixings. Old fastenings on shiny new or repainted parts look horrible. New ones are quicker and more pleasant to use and provide more consistency. I also replace all of the old dirty and clogged grease nipples with new plated ones.





Because this bike was destined to have a 'wasted-spark' ignition system, it needed to have either a dual-output coil or a pair of coils wired in parallel. A dual-output coil was included in the inventory so it made sense to use it. In cases where a customer wants to retain the standard electrical configuration, I will mount the coil inside the electrics box. If, as in this case, the owner has no preference, my inclination is to mount the coil away from the electrics box and in a flow of cooling air, where practical. There are two reasons for that. Firstly, it separates the high-tension coils from any electronic components, such as an electronic regulator, to eliminate possible influence on it by the magnetic field generated by the coil. Originally, that problem didn't exist because the voltage regulator was electro-mechanical.

Secondly, coils can get quite warm, particularly double-output coils, and their performance can deteriorate rapidly if they run too hot. The electrics box is not a good environment for keeping things cool. In this case, as in several others, I mounted the coil slung under the frame top tube, where it would be hidden by the fuel tank.

The final assembly jobs included attaching the refurbished Altette horn, stop-light switch, warning lamps, speedometer, lighting/ignition switch and ammeter, which completed the list of standard electrical components. However, for this bike, there was a requirement for a set of direction indicators to be fitted. Any form of indicators could be considered a deviation from the essence of the bike but many owners feel that the safety advantages outweigh that concern. Even so, choosing a style that doesn't look too out of place and attaching them in a way that is least intrusive helps to preserve the character of the bike.

The front indicators were attached either side of the headlamp shell, using the holes for the original mounting bolts to accept the tubular fixings on the indicator stalks. The wires passed down the tubular bolts into the shell. The rear indicators were mounted either side of the number plate bracket, which required a new hole to be drilled for each indicator stalk, so that the wires could pass into the void behind the number plate. This method results in none of the wiring being visible and routed where access to the main loom is easy. To increase visibility of the lenses from the rear of the bike, the stalks were extended by using the lathe to make a pair of stainless steel threaded tubes. The indicator switch was chosen to be similar in style to the dip/horn switch and it was positioned within thumb-reach of the right-hand handlebar grip.





Once all of the electrical components were in their working positions, work could start on the loom. Fabricating a new wiring loom directly onto the frame gives a better fit and a neater appearance than trying to do it on a flat surface and transferring it to the bike. I stick rigorously to the original wiring/colour scheme unless extra equipment requires additional provision, such as a set of indicators. Then I use a logical addition to the scheme with new colours, so that wires can't be misidentified. For the extra earth wires, I use red for +ve earth schemes and green for -ve earth schemes. They were always +ve earth when they came out of the factory but some owners prefer a -ve earth scheme. It makes no difference at all, of course, unless you want to use a specific piece of electrical equipment that is not available for a +ve earth configuration.

The use of an alternator in place of the original Lucas dynamo makes very little difference to the wiring scheme but one exception is that the charge warning light does not work in the same way. Its function can be restored by using a very small and quite cheap electronic gadget called a lamp driver. It works by comparing the output from the alternator with a fixed voltage threshold value. The warning light is extinguished when the alternator output exceeds the threshold. One can be purchased from Paul Goff and elsewhere.

Although I stick to the standard colour scheme for the loom, I tend to use modern thin-walled wire, which provides ample current capacity for use in either 6V or 12V systems but has a minimal outside diameter. Once the new loom is encased in its protective sleeving, it has a very neat and tidy appearance and a small cross-section. This is particularly helpful when a set of indicators is fitted and five wires need to pass from the rear number plate to the electrics box via the mudguard. This bike will have a 12V electrical system owing to the use of a 12V alternator. A new 12V AGM battery was charged and installed in the battery box, once the loom had been connected up and tested with a multi-meter.

The saddle was a new pattern item that had a pair of new chrome springs with it but it was missing the two brackets that are needed to attach the saddle frame to the frame lug behind the tank. A pair of new brackets were made from flat steel bar, by copying them from another S8, and finishing them in gloss black. The new saddle was fitted onto the frame.

When the painted fuel tank came back from the finisher it looked perfect but it contained a significant quantity of the blast medium from the preparation of the tank prior to priming. It was essential to remove all of that before the tank could be filled with fuel. The tank was flushed several times using hot water and detergent and finally using petrol which was then discarded. The fuel tank, now adorned with fuel taps, knee pads and new badges, was then fitted to the frame and the fuel line attached.





I poured a few litres of fuel into the tank, at least sufficient to do some tests in the workshop and take the bike for a test ride. The engine needs to be running to check for unexpected noises and oil leaks, to verify that the charging system is working and that oil pressure is present. It is also important to get the engine thoroughly hot to facilitate setting up of the carburettor idle settings and to settle the head gasket.

Once the engine has become stone cold again, I always tighten the head nuts again to take up any slack. I find it essential to take every bike that I work on for at least one test ride to make sure that it is road-worthy and performs as it should. It also provides another opportunity, after the engine has cooled down, to tighten the head nuts for the third time. This procedure ensures that the head gasket will have a long and trouble-free life.

The test ride was completed without any problems. The bike performed well, steered straight and handled nicely. Everything functioned correctly and, upon return to the workshop, there were no signs of any oil leakage or unexpected noises. In my world, that all adds up to a successful resurrection of a very nice S8.







The final task before the bike could be delivered back to its owner was to drain the engine oil and replace it with new oil. Even though the oil had done only a few miles, discarding it is an important final precaution to make quite sure that there is no blast medium still lurking in the engine. Did I mention that I really don't like blasting engine cases?