International co-operation

K Kool Transition Model

In the frantic world of competition, motorcycles are constantly developed which means occasionally bikes of one year include bits from the previous year as they transition from model to model.

Words and pics: Tim Britton Media Ltd

Above: KTM’s 1974 GS250 Enduro.

Left: Farioli were the Italian KTM importers. Despite the UK team having its best result in the ISDT for many a year in 1973 and doing it mounted on machines created from the fully road-equipped trail type Triumphs there was little doubt it was a swansong for our home industry. Something more suitable for the changing face of the ISDT, which had become a six-day enduro rather than a shop window for production machines, was needed. Such a statement was no real revelation; it had been clear for some time the rest of the motorcycle world was more concerned with being seen winning on machines often only loosely related to ones which could be bought than promoting their home country products. When the post-event discussions were in the press there was much talk of the smaller, lighter machines used by the Eastern Europeans – however until the rules were relaxed and Trophy teams could be mounted on machines not made in the home country they were stuck. It didn’t stop the team riders trying other machines though.

THE PENTON CONNECTION

KTM’s off-road history is inextricably linked to the American Penton family and a jolly good job too. Very briefly in the late Sixties John Penton approached the Austrian manufacturer with a proposal to make 100cc and 125cc motorcycles for the American enduro market. Penton’s reasoning was a smaller, lighter machine would be easier to ride and not need to be as powerful so wouldn’t tire a rider. The concept was one practised by the Eastern European teams who had 50, 75, 100 and 125cc machines in their ISDT squads. The bikes would be marketed as Pentons in the US and the connection would prove to be beneficial to both parties. KTM wanted to build larger machines, with their own engines rather than Sachs motors, their first – a 175cc engine – was introduced in 1972. It was followed by a 250 one year later then, for 1974, a 400cc unit.

Once the rule changed and opened up the manufacturing world to the Trophy squads – the Vase teams had enjoyed such freedom for a while – the problem was what to choose. Jawas, MZs and such were available but were not quite the same as the respective factory riders would be using. There were others of course, Husqvarna being one with a good track record and the KTM/Pentons had proved their worth but were of small capacity until the factory decided a bigger bike than 125cc was needed and started developing their 175 which grew to 250cc in 1973. This first year was successful for KTM and as 1974 dawned they had their new GS250 enduro model available though it did rely heavily on the 1973 stock of engines. Mauro CipolatGotet, an Italian electrician living and working in northwest England and the owner of this stunning GS250, is telling me a bit about the machine as I photograph it. “I have had it since 1988 and used it in enduros at home in north-east Italy,” he says. “It is a transition model with the engine pretty much as 1973 but fitted to a new frame known as the ‘Tubino’ because of the small tubes making the frame from the footrest to seat area. The next model year has oval tubes of greater section and a black painted engine rather than a silver one.”

How did I come to be photographing such a transitional model far from the owner’s homeland and the bike’s parent factory? Simple, I struck up a conversation with Mauro as we waited our turns at a section in a Cumberland trial a couple of years ago and he mentioned having just started the restoration of his KTM which he brought over from Italy in 2010, would I be interested in seeing the result? Oh yes!

Just at the back end of November 2021 an email pinged up with an image on it… and oh boy! What an image! The accompanying message was along the lines of ‘remember me from…’ and adding ‘this is the bike, are you interested in a feature?’ Then the weather hit… Still, there was one fine day at the end of last year so we took our chances and headed west in the hope the weather would last.

Above: 1975 IOM ISDT 21-year-old Jack Penton, US.

Above: A new cover over the original foam on the original base restored the seat.

Left: Bing’s Type 54 carburettor is also a transition with both choke and tickler.

Now an enduro bike really needs to be photographed in the countryside and Mauro suggested a couple of locations which might work for our shoot. As I took pics and positioned Mauro’s bike for best light I caught up on a bit of background of the superb looking KTM. Mauro has had the bike since 1988 but it was in the workshop at his family’s home in north-east Italy while his work took him all over the world. “I always was going to restore it,” he says, “but until I had a settled base there was no point in starting the rebuild.” Mauro finally brought the KTM over to the UK in 2010, figuring if it was in his garage in the UK it would at least get some work but the project remained on hold until the Covid lockdown altered lots of plans. With time available he set about checking the bike over and found his memory of how the bike was differed from how it actually is. “It had deteriorated a bit with not being used or looked after,” he tells me, “but it was still complete and all the bits which can become lost were still there.” It was however in need of every part looking at and even though the KTM hadn’t had a hard life it was quite worn rather than bashed about. The only thing to do was to strip it down to every last component and start from there. “I have tried to salvage and reuse as much of the original machine as possible.”

Once the bike was completely stripped Mauro admitted to making a mistake. “I was excited to begin the rebuild and had the frame powder coated. I should have done the mechanicals first,” he shrugs. However he didn’t and once the frame was back from the powder coaters he had little option but chalk one up to experience and press on. The swinging arm actuates on needle roller bearings and they were well past their sell-by, as indeed were the cup and cone steering head bearings so both sets of bearings were replaced. The swinging arm spindle was in good condition though and went back in.

In less good order were the suspension units at either end of this stunning machine. Both are Marzocchi and of a high specification for 1974 and both needed a lot of attention to bring them up to the required standard. For the rear units a complete rebuild kit was available and in the great scheme of

Left: Fully rebuilt, rebored, all new bearings and seals with the crank done too, the six-speed engine is ready for action.

Right: Hubs and brake plates are magnesium, both ends only require bearings, seals and cleaning, the shoes were in great condition.

A MEMORY JOGGED

It is a fact of life ‘firsts’ tend to stick in your memory by which I mean things like the first time you cleaned a section, or got the holeshot or rode an enduro. Though equally it could be the first time you saw something momentous such as a Norris rosewood infill smoothing plane or the Slimline Sherpa T I saw when my dad took me to my first trial, these things remain in the memory. The memory may well be buried deep in the consciousness but needing only a slight jog to reawaken it and the recollection of just when something was seen is back like a shot. In this case the memory of when I’d first taken note of a KTM enduro model bounced back large as life. It was Thursday, May 9, 1974, probably around 4.30pm… and in the pages of MotorCycle, week ending May 11, 1974, p14 to be exact. How can I be so precise when remembering what I had for dinner yesterday is not always possible? Because I came across the feature again while feverishly scouring back issues of MotorCycle in Mortons’ archive in a desperate hunt for information about the 1974 KTM GS250. I knew I’d seen something years ago when, in common with thousands of other enthusiasts, the only sources of information we had were the two weekly papers which in pre-internet days were as up to the minute as could be had. Flicking over each page, scouring the pics and words for the distant memory when, suddenly, there it was. Exactly as I remembered it, complete with Ken Heanes in Seventies flares kick-starting a 400 KTM and announcing the UK team would be KTM mounted in 1974’s ISDT. In the end though the team used Jawa rather than the Austrian machines.

Above: Though of aluminium the yokes and headlamp brackets are powder coated rather than polished.

Below: It has taken quite some effort to bring the GS250 to this standard. things it wasn’t long before both rear units were back to pristine with new seals, rods, oil and springs. Up at the front end it was a little more involved and after Mauro had stripped the forks to their component parts and scrupulously cleaned every last bit the stanchions could be sent away to be rechromed. If the hard chrome plate – an engineering coating rather than decorative – isn’t spot on then the chances of a fork seal lasting more than seconds is slight. With the stanchions back in Mauro’s workshop the sliders were fitted with new seals, springs and dust covers before being slid into the fork yokes which had been checked in case they were twisted and, perhaps unusually for aluminium yokes, powder coated rather than polished. Querying this with Mauro I learnt the finish was as per the factory.

With the frame and suspension together it seemed a good time to do the wheels and as an indication on how seriously factories were taking the whole weight thing KTM went from aluminium castings in 1973 to magnesium for 1974. Both the hubs and plates are in this ultra-light material and thankfully were undamaged. Now, by the mid-Seventies most comp bike wheels wore alloy rims and KTM favoured flanged Akront ones which only needed aqua blasting to return them to looking excellent. Now, those spoke things… it seems KTM had their own spokes made 

Plenty of room around the gearbox sprocket and swinging arm to prevent the build-up of mud in an event. Schmid were the chosen fastener suppliers for KTM and others, these days they concentrate on engineered wood screws.

and the ends which go in the hub have a clover leaf pattern on them. I can’t imagine such spokes are thick on the ground and Mauro agreed. “An enthusiast commissioned a batch to be made and I bought a full set from him,” says the lad and the wheels were quickly built and fitted with new bearings and brake shoes for the plates. Finishing off the wheels are new enduro tyres, originally KTM would have used Metzeler rubber and, of course, Metzeler still make tyres but nothing looking like the original type so Mauro has used Pirelli as the nearest to a classic mould to suit the 1974 machine.

Mauro’s decision to save as much of the GS250’s originality as possible is not an easy path to follow and always depends on the condition of what is being saved. Take fasteners for instance; loads of new ones are available in a variety of materials from ordinary steel to fancy aerospace stuff but KTM were supplied by Schmid in those days. Mauro salvaged as many as he could and only replaced the ones too worn to be safe to use. “If I had to replace one I tried to do it where it wouldn’t be seen, if I could,” he explains.

Also saved was the glass fibre petrol tank which, thanks to its shape, is known as the ‘water melon’ tank. It was designed originally for models going to the US and while larger than the MX unit is a smaller and neater tank than the massive ones KTM used previously. Now old glass fibre and modern fuel are not easy bedfellows as the resin used in their construction is softened and the unit delaminates which isn’t good. Mauro has cleaned the inside of this rare tank and applied a liner which so far has held up to the task. Also glass fibre, but not likely to be affected by ethanol, is the seat base. This is the original, as is the foam, but a new cover was needed. However the mudguards, with the KTM logo in, were too badly damaged to save but such things are available from regular CDB advertiser Andre Horvath’s Enduro Klassiker.

While all this chassis work was going on the engine too was being looked at very carefully. Says Mauro: “It is the same as the 1973 250cc engine but housed in a new frame for 1974, perhaps KTM were using up stock, I don’t know. I do know the later models at the end of 1974 had some improvements to them, there

Below: Gleaming in the winter sun, and attracting attention too.

had been instances of damage to castings where kick-start mechanisms had caught them so were beefed up a bit.

Okay, 1973/4 engine, the first 250 unit from KTM’s own factory… was a six-speed unit with primary kick-starting, so no fishing for neutral if the bike stalled. A Motoplat electronic ignition made sure the spark was there all the time and big fins on the barrel and head meant the bike wouldn’t overheat even when plastered with mud. When Mauro stripped the unit he found a lot of wear and when one bit is replaced it makes sense to carry on. So, as well as all the bearings and seals needing replacement the barrel needed a rebore and a new piston. Originally a Mahle piston would have been used, these are so rare as to be considered unobtanium these days so the options are Wiseco and Wossner – having made such a statement I fully expect someone to come up with “just looked in the old stockroom, not been in there for years, full of Mahle pistons…” The barrel was on standard 71mm bore and the first oversize is 71.25 which with the 62mm stroke still comes comfortably under the 250cc class limit.

Ian Ambler, a local lad to Mauro, did both the rebore and the crank rebuild to set this engine back on the path to new life. For 1974 the engine castings were coated black, later in the year the newer castings are silver though. With all the bits laid out on the bench, assembly could begin and soon the engine was together; now KTM aficionados will know of ‘Dimension X’ which is the critical cylinder deck height measurement measured at the top face and adjusted by varying base gasket thicknesses. It can be a long and fiddly process but has to be done. 

Left: Silencer has been de-dented, blasted, repacked and painted with the end cap rechromed.

Above: Though complete this KTM had had a life, not a hard life but definitely used.

Left: Not sure if you can make out the ‘Tommaselli’ name but that’s who supplied KTM with ‘bars.

Below: This side panel was salvageable, the other side had to be replaced.

Once the engine was rebuilt and mounted in the frame Mauro’s KTM started looking like a motorcycle again so work could go on to the ancillary parts such as the Bing 54 carburettor. As befits a transition model the carburettor too was a crossover. The world was beginning to think pressing a button on the side of a carburettor to enrich the mixture and have it dripping out was perhaps not quite environmentally friendly so the choke was becoming more acceptable. The concept of enriching mixtures by reducing the air flow into the carburettor had been around for a long time – even British motorcycles had an ‘air valve assembly’ but backed up by a tickler button. So it is with this Bing as it has both a slide choke and a tickler. Carburettors are tricky things to restore, they’re fragile for a start and Mauro has cleaned his as best as possible but the pilot jet is seized in the body and has resisted all attempts to remove it. “I would try harder to remove it,” Mauro tells me, “but if I damage the body then I’d have to find a new carburettor.” As with other parts of the machine any worn bits in the carburettor were changed and the intake system got a new air filter to fit inside the original glass fibre airbox which sorted out the intake side of the engine. Getting the gases out was more involved as the exhaust system on an enduro bike can often suffer damage if there are any incidents. Careful cutting and delicate work beating the damage out then welding the pipe up again will cure most damage but it is a long and involved task. While on the exhaust it was repacked and the end cap chromed. In fact all of the bits which would have been chromed originally have been rechromed.

The Tommaselli company – now Domino – supplied KTM with handlebars and these were reused, as were the Magura controls, while cables came from CIF in Italy and Venhill in the UK. An enduro bike has a headlight and tail-light as standard equipment and requires a wiring harness to connect both to the power supply… when your trade is as an electrician such things are not difficult to make. It might have been more cost effective to buy a harness but this way Mauro could remain faithful to the original colours. The KTM needs some final fettling to set things up but fired up reasonably quickly on the day we were there. Because of the high ethanol content in petrol and its effects on older machines Mauro keeps the bike dry internally so it took a while for the fuel to work its way through – but once running the bike sounded great as well as looking superb.

Above: While every effort has been made to retain original parts some bits just had to be replaced.

Below left: A welded loop guides cables safely and stops them snagging.

Below: The slight dip in the tap mounting helps keep fuel in the right place.

Below right: Rebuild kits were available for Marzocchi shocks, anyone know if they still are?