1948 KSS / 1954 MAC Special
My Special originated from the well respected South Australian Velocette agent, Lou Borgelt. To a purist it was a lovely motorcycle, but to me, with it's strange green paintwork and plastic Velocette tank badges, it's only redeeming feature was it's spring frame and telescopic forks! The alloy motor no longer sported the original cylinder barrel by the time it passed into my hands in the mid 60s.
I first saw it when it arrived on Kangaroo Island in the hands of a local spoiled teenager who had just obtained his riding/driving licence at 16, the state's legal age. The bike was secondhand but had just been rebored and fully serviced by Borgelts, and was like a new machine. However in the hands of it's irresponsible new owner and his mates, plus the fact that the Island's roads were a lethal mix of seldom graded ironstone rubble, winding bush tracks, and fine abrasive dust, and of course the bike lacked the refinement of an air filter, the engine was soon seized several times to the point where a new barrel was fitted, and then a second one, then a third iron barrel because of the lack of alloy spares, this soon degrading to the point where the owner lost interest and bought a car!
It was more than 10 years later and I had left the Island and moved to Melbourne, then with the resurgence of interest in motorcycles, due mainly to the Japanese invasion, I decided that during our annual Christmas vacation to the island, I would with the help of my five now motorcycle mad children, make an attempt to gather up the remains of all the bikes that I had previously imported to the Island, and sold at cost to the local lads when we formed the now long defunct scramble club back in the mid 50s. In the process, the MAC became mine for the sum of $4!
It had changed hands previously in a non-running state for $10, but the generator had been removed by the new owner's children and made into a wind generator, then subsequently lost somewhere around the farm. As it had been stored in a living chicken house, only the rusted seat pan remained with a few odd chunks of the original foam, and so the owner felt that the value had dropped to $4!
This wasn't surprising when you considered that I was buying complete Ariels, AJS's, and Nortons etc for around $20 for potential runners, and I think the most I paid was $35 for a clean Norton that had been registered up until recently. Some machines cost nothing, but entailed the efforts of us all to rake the dismantled remains out of tall grass and the grime of farm storage sheds.
The MAC's silencer box was long gone and the exhaust pipe was unrecognisable, but the money changed hands and amazingly, the old owner turned up at our camp site the following year with the generator and regulator plus the old battery and clamp parts, only wanting a ride on our new Yamaha trail bikes. A look inside the motor revealed a completely shot bottom end and of course a ruined barrel and piston. It didn't take me long to decide that a good complete '48 KSS motor that I had would be checked out for size in the frame!
The well known problems were soon assessed, anyone who had done this conversion before had used the earlier gearbox as the only option, but I was not about to forego the series 12 gearbox, and it didn't take me long to reach for the hacksaw and cut through the two bottom frame rails, which immediately sprang apart almost enough to allow the KSS motor to bolt into the original MAC gearbox/engine plates. Only a little pressure was necessary to allow the generator to be put into place, and a temporary packer to be put between it and the front frame tube. A pair of new front engine plates were made and everything bolted back into place, where it was determined that two mild steel spacers with the end diameters turned down to the inside diametre of the frame tubes, and the main centre section turned to the outer diameter of the frame tubes, and chamfered to permit good arc weld penetration to the frame tubes, the overall extension of the bottom tubes being in the order of ¾ of an inch or about 20mm.
At this point it was noted that the KSS motor had assumed a slight forward tilt, but as this gave more clearance to the decompressor mechanism to the petrol tank, and also fractionally more clearance from the gearbox body to the KSS magneto chain case, it was ignored.
The new front engine plates were unbolted, and the frame sprung open to allow the spacers to be inserted in the frame tubes, the engine plates replaced and everything bolted up tight and checked, and then the whole plot was rolled around on the floor while the tube spacers were welded where clearance allowed. The engine and gearbox were then removed and welding completed and ground smooth.
The only major work was to modify the primary chaincase to accommodate the engine/gearbox mainshaft centres which had increased by about 10mm. At first this looked like being the considerable labour of lengthening the entire chaincase, but it became apparent that there was enough room to move the engine sprocket forward in the front of the cases, and still allow chain clearance which was diminished, but still sufficient.
The sheetmetal parts around the mainshaft hole were removed by destroying the parts, and grinding the old spot welds in the cases smooth. New parts were turned up from solid steel stock with the oil containment arrangements improved by the addition of an internal groove and an oil ring to seal the case to the crankcase main bearing boss. The primary case and all related parts were given a dry assembly, and the new mainshaft sealing arrangements were put into place, and rivet holes drilled, everything then dismantled and the new rings riveted into place and soft soldered. I cannot remember small details, but the hole in the cases had to be elongated forward I think, and the new rings that I turned up needed to be larger in diameter on the contact faces to allow sufficient meat for riveting and soldering.
The only other detail that arose was that the mount bolt that goes through the primary cases was no longer in the same location to the frame lug, it also having moved about 10mm, but this was easily overcome by turning up a solid plug with the original central hole offset approx the needed 10mm.
The decompressor arrangements were reversed, the cable and casing anchorages transposed, but it was still necessary to hammer a depression in one of the bottom tank welds. Many years later when the bike was fitted with a lightweight Velorex sidecar, the opportunity was taken to cut a section of the underside of the tank away, and weld in a new section to give much more clearance to allow access to the cable adjustment.
Not long after the bike was put on the road, I was unfortunate to have a Sunday morning churchgoer drive through a stop sign at a road junction, and just to complicate my life further, as I was doing my best to avoid him, did a u-turn 'across my bow' in his attempt to enter the church driveway. I hit him just forward of the rear wheel and sailed across the car's rear deck, luckily without damage to myself, but bent forks and a wrecked tire, tube, rim and spokes, saw me spoking a 21 inch front rim to the undamaged hub. I had been considering making the modification and had all the parts on the shelf.
The mudguard and stays were completely wrecked as well, and partly as a result of reduced clearances with the rebuilt wheel, I found myself using a small narrow guard and a very light support arrangements, which cured the previous stay breakages completely due to the reduced mass weight.
The original rear guards had been split across the valances when I bought the bike, this due to the unfortunate natural shudders that is peculiar to some of these Velocette models at engine idle and low RPM. Then after unsuccessful repairs, I hit on the idea of making a pair of flat braces which are carefully bent to bolt at the back of the 'arcuate slot' frame section to the lower edge of the valances, where a single bolt and large aluminium washers clamp the valance solid, and completely eliminate the shakes. I never even welded up the fractures in the valances, the flat washers holding the entire rear end of the guard completely solid, and the fractures hidden under the large washers. It remains the same to this day!
As the bike was used continuously from it's original build, I added improvements from time to time. First was a modified set of Yamaha turn indicators, operated from a Honda stepthrough postie bike handlebar unit, which also provided better switching arrangements for dip and horn.
Later the move to a modern plastic case battery, led to the making of an oil tank 'reversed image' cover to hide it, and so the battery tray was modified for the smaller dimensions of the new battery and two bolt anchorages were provided for the new cover at the base. The top of the cover has a single bent steel rod peg which anchors firmly in a rubber grommet, in a hole at the top of the battery tray anchorage plate.
The magneto had a kill terminal on the points cover, and while a knowledgeable thief only has to remove this to start the machine, I decided to incorporate a Yamaha trail bike keyed switch on a bracket on the battery tray, the key accessing the switch through a hole in the new battery cover. This proved to be very useful some years later when the sidecar was fitted, and also a car type alternator mounted on the front of the sidecar chassis, the switch had the ability to power up the alternator circuit, and the addition of a red idiot light in the headlight cowl, the possibility of a drained battery was avoided. The system was of course, changed to 12 volts at this time and a driving light was fitted to the sidecar chassis, powered from the high beam circuit, with an isolation switch and a blue idiot light to indicate that it was in circuit. The 12 volt battery was of identical dimensions to the previous 6 volt, so involved no mounting changes.
Another cosmetic item was a simply made sheetmetal cover over the engine/gearbox mount plates, this was secured by a single ¼ bolt to one of the plates in a tapped hole that was already there. The worn out ammeter was replaced by a 12 volt Jaeger that had once graced the dashboard of a British car! Other improvements were the fitting of Japanese petrol tap with inbuilt filter, the removal of the plastic tank badges and the recesses filled with soft solder, the original seat having being destroyed during use as a chicken perch, a complete brand new Loch Ness seat with torn cover was sourced from Frank Mussett, and he graciously donated it to the project, and a friend in the Victorian Velocette club recovered the seat in a tasteful heavy duty vinyl, beautifully stitched, a credit to his workmanship to this day.
I decided that I just had to have the old style silencer box, but was aware that it was impossible to fit one to a S/A frame without it either sticking out at an odd angle, or having to be mounted too far back to please the eye, and so I made a new silencer with a convenient depression on the inside to clear the bottom frame loop, and a much better two bolt mounting – one from the pillion footrest bolt, and the other rigidly supporting the pipe clamp at the front, the bolt in this clamp being an extension of the centre stand pivot shaft. The silencer is in fact slightly smaller in it's dimensions, but no one has ever remarked on this!
The addition of the sidecar should have included stronger front fork springs, but somehow I never got around to it as the plot handles well without some of the exertion needed for some of these set ups. However, it did suffer from uncontrollable lock to lockers at starting off speeds and so I decided to make and fit a friction steering damper of the old design, and this completely cured the problem with very little pressure needing to be used at any time.
When the sidecar was fitted, I decided to make a bracket to extend the seat mounting point further back on the frame to keep it away from my leg, this cut down on the bracketry and this custom mounting point is very much neater. The alternator is V-belt driven, and all the original generator components have been stored.