Sunbeam S8 – Full Restoration




Part One of Three – Dismantling and Preparation



Most customers send their bikes to me via a courier and brief me on what they want to do via email or by phone. Cliff, however, brought the bike personally in the back of his van and we spent some time talking, over a mug of tea, about the bike, its history and describing his vision of what he wanted it to look like after restoration.

This wasn't to be a recommissioning or repair job but a full ground-up restoration to take the bike back to the way it would have appeared, proudly displayed in a showroom in 1952 but with a higher quality of finish. The primary emphasis was on the appearance of the bike. Some wear in internal components could be tolerated, provided that the mechanical integrity will remain sound for many thousands of miles to come.

Cliff bought the bike a few years ago as a project. It had been restored some years before but not to a high standard and ridden very little before being stored in an unsympathetic environment. The paint was close in colour to the original Polychromatic Gunmetal Grey but was of poor quality, the base colour having been sprayed and left without a protective lacquer finish. The chrome was cheap and cheerful and had pitted in places and showed surface rust in others. The impression was of a basically sound bike that had acquired a little too much patina.





Over a period of a few weeks, Cliff and I discussed how to get as close as possible to his vision without unnecessary extravagance. It was agreed that the frame and a number of less visually important parts, like engine mounts and brackets, would be powder coated with a gloss black finish. We pondered the merits of stainless steel or chromium plating for wheel rims and exhaust pipes and we discussed what shade of grey the body parts should be. Initially, it seemed natural to revert to the original colour that Sunbeam had chosen, many years ago. However, when I sent a paint sample to Cliff for him to look at, he concluded that Sunbeam's choice of grey was no more inspiring than their choice of green.

That led to a search for another metallic grey paint that is sufficiently close to the original colour to look authentic but much more appealing, particularly in bright sunlight. I acquired some more paint samples for Cliff to consider and he chose BMW Space Grey, a freely available, robust modern paint with a deep metallic shine.

The restoration started, as they all do, with stripping the bike down to its constituent parts. I always clean and wash parts before bagging and labelling the small parts and assessing the condition of the larger parts as I set them aside. I don't like handling dirty parts and I don't want them to drop filth on the work bench or on the floor, so cleaning always comes first. It also helps a lot when assessing the condition of components.

Bagging and labelling is vital if, like me, you work on several bikes in parallel. I also use separate parts bins for each bike but the labelling provides a second line of defence in case a bag is placed in the wrong bin. These things can happen and looking for misplaced parts can waste a lot of time if you don't have a reliable system.





The next task was to decide what needed to be discarded and what needed to be repaired, renovated or replaced. The cycle parts were divided into six basic categories: grey shiny parts, black shiny parts, black structural parts, chrome parts, stainless steel parts and fasteners. There were a number of stainless steel items that had been fitted during the previous restoration. They were all in excellent condition and needed little more than a gentle polish on the buffing wheel to refresh the shine.

Some chrome parts had been re-plated during their previous restoration but the quality of the chrome was poor and it had not aged well. Good quality chrome is a joy to behold but is expensive.

Even a fairly simple bike like a Sunbeam takes up a frightening amount of space when it is stripped right down to its smallest components. It was a priority, therefore, to get as many parts as possible out of my workshop and delivered into the hands of blasters, finishers and platers, for them to work their magic.



At this point I made what turned out to be a mistake. I took the parts to a blaster and powder coat finisher that I had not used before. They sounded convincing and boasted of their particular experience with motorcycles but their preparation and finishing turned out to be poor. Some parts had been blasted too aggressively and the surface has been left pitted. That can sometimes happen if a painted surface conceals corroded metal beneath, so it isn't necessarily the fault of the blaster. Their sin lay in the subsequent coating of the pitted parts without either remedying it or speaking to me first.

I really don't understand how a craftsman who takes pride in his work could possibly do a thing like that. Did they think I wouldn't notice? I decided that, in future, I will leave that particular company to apply their skills to iron railings and garden gates, while I sought out a better finisher.




Fortunately, the rather more capable, and inevitably more expensive, finisher that I had already asked to do the grey painted parts was happy to take on the job of rescuing some of the powder coated items that the previous finisher had rendered less lovely than when he received them. Unfortunately, the front and rear mudguard stays were so badly pitted after blasting that they were beyond economic rescue. The solution was for me to reproduce a complete set of stays in new seamless steel tubing. This required dismantling the rear stays so that the cast lugs could be re-used. I brazed these, and the newly made lugs for the ends, onto the pre-formed tubes and the complete stays were powder coated properly.

With luck, the complete but unfinished rear stays can be seen in the picture close by, ready for priming and painting. The rear stays were the most complicated to fabricate because they involve a number of awkward angles, The pressed lugs at the ends were made with a pair of steel dies in a hydraulic press. Simple enough but each of the three lugs on each stay are in a different plane and the bends in the upper tube are in yet another plane. A geometric puzzle for sure, which involved a lot of checking and rechecking before they were ready to do a trial-fit to the bike frame.



Part Two of Three – Repair and Refurbishment

Not all of the black parts were to be powder coated. The wheel hubs and the rear suspension shrouds, for example, were painted in gloss black to give a more authentic look and a high-quality finish.

The tinware was all in pretty good condition but there was some preparation work to be done before the grey parts were ready to go to the painters. Some rust holes in the rear mudguard needed to be welded up and one or two more holes appeared during blasting. The fuel tank, although in good condition and leak free, had some surface rust on the inside and needed to be lined. A previous failed attempt to line the tank with epoxy resin had to be dealt with first. I ordered a bottle of unpleasant chemicals that claimed to be capable of dissolving the resin. I was relieved to find that it was extremely effective, if a little unpleasant to handle and awkward to dispose of.





Some parts were not cost-effective to re-plate. Even though the wheel rims were sound, it was cheaper to buy new ones than to have them re-plated. The same applied to the exhaust down pipes. I acquired a pair of Elite Chrome rims from Central Wheel Components and laced them up to the newly painted hubs with new stainless steel spokes, also from CWC. The Exhaust pipes came from Armour. They looked good and fitted perfectly.

Cliff and I agreed on chrome, rather than stainless steel, for the rims and pipes because they would give a more authentic look. However much you polish stainless steel, it never looks quite the same as chrome and it ages differently.

When the grey parts came back from the finisher, they looked splendid, with a lovely deep shine, especially in daylight. But they needed to be carefully wrapped in protective foam sheeting and stored out of reach of accidental damage until the frame was ready to accept the body parts. The high cost of a good quality paint job justifies taking a lot of care.

Whenever I send parts to service providers to have work done on them, I catalogue the items and take photographs of every one. I have heard enough horror stories of irreplaceable parts being lost by the chrome plater or sent to the wrong customer by the painter to make it well worth spending the time to take precautions. I send copies of the pictures and the schedule of parts along with the parts themselves, as a reference in case any issues should arise.





In the mean time there was work to be done on the engine, gearbox, rear drive, front forks and rear plungers. Starting with the engine, the cylinder block and cylinder head had to be stripped down to the bare castings so that they could be vapour blasted.

Vapour blasting is the best form of blasting for Sunbeam engine cases. It preserves the original texture while removing dirt and stains.





I don't normally like to blast engine cases because of the risk of contamination by the blast medium. But it is very hard to achieve the brand new look by any other means on a casting with deep finning. The gearbox and rear drive castings, on the other hand, were re-endowed with a youthful appearance with the aid of degreaser, Scotch-Brite, a stiff brush and 1kg of elbow grease, which I sourced from eBay.

In any case, stripping the engine down to a bare casting provided a good opportunity to examine all of the internal components and mating surfaces for wear and damage. I made sure that the blasting was done to the outside surfaces only, to reduce contamination, but it still meant that a great deal of care was needed in cleaning the castings when they came back to me. A lot of scrubbing ensued and a whole tank full of solvent, together with the filters from the tank, needed to be discarded afterwards. Even so, as an additional precaution, the first sump full of engine oil was discarded and the filter was scrubbed as soon as the engine had been warmed through from its first start-up following re-assembly.

The engine had not done many miles subsequent to its previous rebuild. The bores and pistons were in pretty good condition, showing very little ovality or scoring, so Cliff asked me to fit new rings and hone the bores.

The crank, on the other hand, had significant scoring on the rear journal as a result of debris having found its way into the oil after its last rebuild, so it needed grinding and new shells fitting. The debris was probably swarf, left in the engine as a result of inadequate cleaning. The scoring probably occurred during the first few seconds after its initial start-up.





The rear main bearing was in excellent condition with no more than light staining on the journal, which I removed with fine emery. Removal of the front main bearing was necessary, as always, to extract the core plug and clean out the sludge trap. I take a lot of care when cleaning sludge traps. Once they have been disturbed, they need to be left spotless. A new core plug and main bearing were fitted as a matter of course.

The camshaft was worn and needed to be replaced but the cam followers were not too bad and were recovered by grinding out the small marks and restoring the curve to the correct radius. I prefer to grind cam followers if I can. I have seen cases where the Stellite has chipped off of refurbished followers, causing damage to the new camshaft, so I only use refurbished rockers when really necessary.

The valve guides, valves and valve seats showed little sign of wear or damage. Just a light lapping-in of the valves was all that was necessary.





The threads on the front centre cylinder head stud and the large centre rear stud on the engine block had been damaged through over-tightening, a common problem on these engines. Repair was effected by drilling, tapping and fitting a steel thread coil to each one. The drilling and tapping were done on the milling machine to ensure that the holes were precisely centred and perpendicular. If a thread repair is not fitted quite straight, the head can be difficult to re-fit and the new thread can be damaged as the stud is forcibly pulled straight when it is tightened. This is another common occurrence. I have had to make threaded steel inserts to fix bodged thread repairs several times.

All of the oil seals needed to be replaced in the engine, gearbox and rear drive since they had all become brittle, through age, and had ceased to function. Time does not respect oil seals. Their condition and effectiveness is usually determined by their age rather than how many miles they have done.





Part Three of Three - Rebuilding



Many small cycle parts had to be cleaned, prepared and painted before reassembly could start. Some required dents or creases to be knocked out or filled. Parts that were beyond being reclaimed were replaced with new ones. The stainless steel parts were polished with a rotary mop to remove small surface scratches and scuffs.

Threads were restored with taps or dies and many fasteners were replaced with new ones of the correct type. The fuel taps were dismantled and new seals made from a rod of PTFE, a much more reliable material now that good quality cork is harder to come by. A new fuel pipe was made from braided hose.

Cliff, the owner, decided to retain the original Amal 276 carburettor, rather than adopt the, often preferred, 600 series alternative. The carburettor on this bike was in very good condition and functioned perfectly well. It just needed to be cleaned and some renewable parts replaced. Apart from the unfortunate design issue with the float valve on the 276, it is made from much more robust materials than the Concentric and, of course, looks more authentic.



The wheels were dismantled and the rims and spokes discarded. However, once cleaned up, both the rims and spokes were good enough to be re-used on another project, to repair a bike that had suffered road accident damage. The hubs were in good condition and the bearings were re-usable but they had to be removed prior to blasting, after which some pitting was revealed on the outer surface of the rear brake drum. Some filling of the surface was needed before they could be painted in gloss black. Rebuilding of the wheels was straightforward, using stainless steel spokes and new, high quality Elite Chrome rims from CWC, to lace them up in their original patterns.

Once the engine was back together and all of the cycle parts sorted, it was time to reassemble the bike. I always find this a nervous time. Great care is needed to avoid damaging new or refurbished parts, particularly painted parts. It is a slow process, made slower because of the need to protect the parts that have already been fitted from damage by the parts being added. The fear of tools slipping or being dropped onto a vulnerable surface is constantly present and precautions are needed to prevent it.



The first stage of assembly seems to comprise little else but the removal of excess paint and powder coat from threads, drillings and mating surfaces. Very little progress is visible during this time but it is necessary ground work that saves a lot of frustration later. Fitting the centre-stand and side-stand, engine mounts and a multitude of brackets, studs, grease nipples and so forth doesn't seem to add much, in terms of visible progress, either. In fact, the ratio of work against progress seems to remain disappointingly low right up until the time when the forks and the rear suspension go on. Only then does it start to look a bit more like a bike.

The first major breakthrough comes when the wheels and the handlebars are fitted. That's a big step change and, for the first time, gives a feel for how the bike will look. The best bit for me, though, is slotting a beautifully clean and shiny (but not polished) engine and gearbox into the black frame. That's when it all comes alive.

One of my pet hates, along with the over-tightening of fasteners and the excessive use of sealant, is the polishing of aluminium engine cases. I like them to look clean and bright but not polished.

Polishing destroys the rugged Sunbeam surface finish, which for me is an important part of its character. Once the surface is smoothed and polished, that bit of character is lost forever. And, in my opinion, polished aluminium castings look quite out of place on a Sunbeam.



Once the main shiny grey parts were on, there was no time to admire the gorgeous paint because it was time to start thinking about wiring. The old loom was tatty and had some scruffy modifications and repairs. It had been loomed with sticky tape in places, which becomes very horrible with age, so it would not have been appropriate to use it as it was. The most cost-effective solution was to make a new loom, using the original colour scheme, but with modern heat and abrasion resistant black sleeving. I used the opportunity to add some extra earth wires to the loom, removing the need for reliance on the frame to provide the earth connections. That is particularly helpful when the whole bike is covered in new paint – a very effective insulator.

Additional earth wires were run from the headlamp shell, from the rear light, from the battery and from the engine and they all converge on the electrics box, where there is a central common earth point.







A number of small electrical parts had been afflicted with rust or damage and had to be replaced. In particular, the warning lights were replaced with new ones. The ballast wire was removed from the body of the lights and replaced with new wire of the correct resistance, so that the lights were bright enough to see in daylight but not dazzling in the dark, still using the standard bulbs. So that the speedometer would not spoil the appearance of the headlamp shell, it was treated to a new face of the right type and a new pointer. The bezel was already in perfect condition.

Originality was a consideration throughout the restoration of this bike but not an obsession. Practicality and reliability also had their place. The finished bike is stunning. It is clean and shiny without being excessively polished, and with an attractive deep metallic lustre, which is not very far removed from the original colour but looks vastly better. It looks particularly nice in bright sun light. But then, so does everything else.