Super Profile
A works bike has a certain mystique about it, surely it must be special…
Bultaco and Sammy Miller are synonymous. We went along to check out Sammy’s last works 250 Bultaco, freshly restored.
By his own admission Sammy Miller was no longer at the top of his trials career in the early Seventies, having pretty much dominated the Sixties, first with his highly developed Ariel based 500cc single, then – to the disbelief of the feetup establishment – he went Spanish and carried on winning. Retiring from major competitions didn’t mean he’d retired from development though and was still a contracted Bultaco rider who would become involved with the 325 Sherpa, before heading for Honda in 1974.
The smart green Sherpa we’re looking over in the courtyard of the Sammy Miller Museum is effectively his last works 250 Sherpa. Though supplied direct from the factory, Sammy did make a few modifications, which brought a wry grin to his face as he recalled them: “Looking back, Snr Bulto was very lenient with my modifying bits and pieces, for instance I didn’t really mod my Ariel until it was out of production and BSA riders had to use what was on the production line.”
So, the frame on this 250, while similar to the production one, is Sammy’s own Hi-boy aftermarket and as such made from Reynolds 531 tubing which made it considerably lighter than the standard model. “It’s also got a thin alloy bash plate underneath rather than tubes, it’d be another few years before the production bikes got that mod,” he says.
Was anything frowned upon by the factory? “Yes,” he grins, “the front hub on this model is full width and heavy, I tried a single-sided 5in diameter hub from a Zundapp I think, which was much lighter. After it was pictured in a paper I got a letter from Snr Bulto suggesting I revert to the Bultaco hub while they got on with developing their own lighter version.”
Miller only rode COT 6K for about a year as he was helping to develop the 325 after making a suggestion to the factory about increasing the capacity. “Bultaco always liked to keep ahead of the opposition and with Montesa and Ossa starting to do well it made sense to look at a bigger engine.”
So this Sherpa is a 250 and is to the standard bore and stroke dimensions of 72mm x 60mm which gives 244cc. To my “is it all standard inside?” query, Sammy said: “Yes and no, first thing we did when it arrived here was to pull the engine apart and check everything over very carefully, particularly the porting and ignition timing.” The engine has transfer ports in both the barrel and the crankcase which, if not matched correctly or accurately will have a considerable effect on the performance of the engine. While production engines are close enough there has to be some tolerance allowed otherwise the cost is bumped up ridiculously high. While he was doing this Sammy also made sure the ports were as close to the blue-print design as possible.
“We did other things too, such as smooth the case off round the drive side area as the standard casting has a lip all the way round, the same basic casting is used for a couple of engines and some have more ‘case’ around that area, all we did was clean it up a bit and make it look nicer, yes it saves a gram or two as well.”
The 250 Sherpa of that era is a ‘close-fin’ engine, the 325 was the first with wide fins, if you look at the cylinder head on this bike there are a lot of gaps between the fins. “I took out each alternate one which helps let the heat escape and again makes it a little lighter too.” Sammy goes on to say the weight saving on individual components might not be huge but they do add up to a significant saving, but he appreciates not everyone has the time nor inclination to do what he does however, and this is my observation, such dedication could be one reason why the Miller name is on so many trophies.
As we chatted about his bike, Sammy pointed out various bits and pieces which might not have been obvious – the distance pieces between the wheel bearings are alloy for instance and can’t be seen unless you’re there when bearings are being changed. Also alloy rather than steel are brake actuating arms. “They were steel but we had alloy ones made up and the correct spline broached in.” In case you’re wondering why all this sort of thing had to be done, perhaps a word on the situation in Spain at that time and under what constraints the factory had to work to would clarify things. Under the rule of General Franco the Spanish industry had difficulty importing raw materials and often bikes had to make do with basic quality metals – hence Sammy making higher quality components for sale. The frame was changed for a ‘531’ type, the top yoke was of better material than the original, a tubular
rear brake pedal was made and the swinging arm had provision for a chain oiler. This was simply a series of drillings so the arm could have oil poured in and a metered delivery dripped it onto the chain. With trials being longer in duration that those today, such auto oiling paid off in terms of reducing chain wear.
Once fettled to his exacting standards, Sammy put the bike to good use and his winning ways continued. “I liked the 250 engine as it was a much smoother one to use, sometimes I used to run an oversize piston which put the capacity at 252cc and qualified me for the 500cc cup in star trials, but the capacity increase, while enough to satisfy the regulations, didn’t affect the engine power delivery too much.”
As already mentioned, Sammy was still a contracted development rider and when Bultaco acted on his suggestion for a bigger engine COT 6K was retired and all focus went on the new machine. The bike was sold on and even though it was last year’s bike, a Miller Bulto was still a handy thing to own. There is a danger that such bikes become playthings and are used and abused, but it seems this particular one escaped that fate.
“Checking it, or any bike, over after we got it back here is always an interesting time,” says Sammy, “is it wrecked? Are there bits we’re going to have to find, plus loads of other things. In this case it was a pleasant surprise as the Bulto seemed to be quite undamaged.”
As might be expected, there are a number of special bits which, while not unique, do add up to making the bike what it is. If these are missing or damaged beyond repair then the task for restoration is so much harder.
Take the frame for instance, lightweight tubing and nickel plated – on inspection there were some cracks evident but it wasn’t until the plating was removed around them could it be confirmed they were in the parent metal or just the plating. It was a case of some of each and the only safe thing was to remove the plating, weld up the damage and replate the frame.
“We were lucky in there was no damage other than a crack or two, had the bike been used in rocky terrain it would have been different.” The swinging arm bushes were replaced, so were the steering head bearings and the frame was ready to build the bike around. It was the same with the forks, little wear, the stanchions were rechromed, the sliders polished and new seals fitted. Once assembled they were ready to be fitted.
“The top yoke on this one is one of our high tensile alloy castings which we did because the standard part was not brilliant. We spent a lot of time making sure the internal taper on the yoke was compatible with the top taper on the stanchion otherwise the forks won’t stay in position. At this time too the bottom yoke was a steel forging with a single clamp bolt to hold each leg in place. This was okay and once painted and a new bottom bearing race fitted, it was ready for use.”
At the other end of the frame the rear dampers needed painting and as can be seen they’re not exactly standard looking Girlings. Being sealed means it’s not an easy job to fettle them up from the inside. The majority of the units supplied by Girling would be crimped at the top though there were competition
units which could be serviced by the factory and these had a removable top allowing the seals to be changed and fresh damping fluid put in. In this case they were still in good order which is a good job. Note the extension on the bottom – a slice of tube welded in to extend the units, “we did that because we couldn’t get the right length from Girling,” says Sammy. These days it would be reasonably easy to have whatever length you want made, but back then there were but three lengths – short, medium and long.
Bultaco used a chrome lining on the insides of the hub as a braking surface and while light and okay in warmer climes, didn’t always stand up to wetter conditions. I know from personal experience the plating on one of my Bultos didn’t last all that long, less than a year, yet on my 250 it was still in place 20 years on but once it did go it seemed as if it all fell off at once. The traditional way to solve this is to replace the chrome with a steel liner but for my restoration I found a place which did metal spraying and the surface was recoated. This Bulto needed neither and the surface was good to go. New bearings, the alloy spacers cleaned up and the brake plates fitted with new shoes once they were polished, sorted the hubs. Lacing the hubs to polished flangeless rims using butted spokes as Bulto did, then fitting new tyres, finished the wheels off.
In the days before we used plastic for mudguards the hot tip was aluminium alloy, which is okay but can be high maintenance, too rigidly mounted and it will distort or crack with vibration, too loose and the mounting holes will wear. When new, a Bultaco would have rubber washers between the mounting brackets and the alloy but these often vanish over time or a different length bolt will be used and the guard squeezed, then there’s the inevitable ‘off’ which can also distort the guard. Look at the rear mudguard on COT 6K, the numberplate is pressed into it… “we made up a special former to do that, it looks a much neater job than another plate on top of the guard, thankfully we could save this one as we’ve no idea what happened to the former.”
Other cycle parts which could be salvaged included the full exhaust system, the front box just needed repacking and painting while the alloy back box was polished up. Even the tank was okay and obviously hadn’t had any of the modern ethanol-based petrol left in it. In fact as soon as our test session was over the tank was drained and flushed out, just in case there were any residual fuel problems.
Turning to the engine it was fully stripped, the cases were polished, the barrel painted black and the head silver. “The big end was okay but the mains and gear box bearings were changed, new seals obviously,” says Sammy, “and it was put back together quite easily. The bore and piston was fine too, new rings were all that was needed.”
After telling me the fasteners were a mix of either replated old ones or newly made Bultaco ones, Sammy jumped aboard, gave decent prod on the kick-start and rode the freshly restored bike round the courtyard. As he came back, a screwdriver was produced and the carburation adjusted, another brief ride then the Bulto was handed over to me to try.
It goes very well, the cables and controls are silky smooth in operation and the bike steers perfectly. I did get a go over some practice sections, nothing too taxing mind you but enough to get the feel of the bike and it goes to show what attention to detail can do. Yes, the suspension is early Seventies, but state of the art for that time; the clutch isn’t a one-finger operation but in those days we didn’t use the clutch while in a section. Opening the throttle made the bike move without hesitation and the riding position was superb.
“I was always particular about moving the footrests of my bikes further back than standard,” says Sammy, “even when I was riding a James in Northern Ireland, the footrests were back in line with the rear tyre.”