Your challenge is…
Traditionally, Greeves bought engines from Villiers, stripped them and replaced most of the bits with their own… until a casual comment challenged that.
… to take on the might of the European and Japanese industry on the MX tracks of the world… enter the Greeves Challenger.
As the biggest supplier of engine units to the British motorcycle industry, Villiers could sell any and every unit they produced, but while an ideal business model, such success doesn’t always go hand in hand with new developments. Nor it seems were Villiers all that keen on supplying partengines, it was an all-or-nothing system, though to be fair this had sufficed the industry for a good number of years. With most of their smaller manufacturer clients being interested in or involved in the off-road or competition world, engines supplied to them were being increasingly modified in order to keep up with the competition appearing from abroad.
This situation wasn’t too bad when the mods involved casting a few alloy barrels to offer as an option over cast iron ones, but by the early Sixties Greeves for instance were abandoning a large proportion of the engine and replacing the bits with their own. A casual comment by engineer Brian Woolley querying why Greeves didn’t make their own engines as they pretty much chucked all the Villiers bits away, resulted in the Greeves Challenger – the first wholly Greeves engine.
Or perhaps, more correctly, a wholly Greeves-built engine, as the crankshafts came from Alpha; Stefa
– the Swedish ignition manufacturer – provided the sparks though Greeves were a little coy about naming them in contemporary reports on the new motor; and Albion provided the gearbox and primary drive. Unfortunately the Albion ’box and drive, more suited to a lightly stressed roadster, was not always able to cope with the increased power from the new Challenger engine in the cut and thrust world of scrambling.
Other ideas
There were several attempts to deal with this and redesigning the change mechanism worked to some extent but other ideas outside the factory were tried. These involved fitting a different and stronger gearbox to the back of the Challenger engine. Eric Cheney did just this modification when building a rolling chassis around a Challenger, he was well aware of the failings of the Albion ’box and the robustness of BSA’S Victor MX gearbox, happened to have a scrap Victor motor so cut the gearbox bit off and fitted it to the Challenger. Ultimately the bike wasn’t a success as the gearbox leaked oil terribly but it gave an idea to Robin Humphries of REH fork fame. Robin spotted the potential and made a few conversions with BSA parts and castings.
What this means is while rare in the extreme there are a few Greeves Challengers out there with a BSA gearbox in place of the Albion one, though determining exactly how many were produced is not an easy task. Former Greeves man Mike Jackson is possibly best placed to hazard an educated guess on the quantity made and that’s where our ‘a few’ comes from. You see Mike was involved in the Eric Cheney Challenger project and actually bought the bike from Eric once it was clear Greeves weren’t keen on continuing with it. Mike told us he tried for a full season to make the bike work properly but oil-tightness of the gear box was always a problem.
Mike happened to be speaking with Robin Humphries who had contacts to cast his fork sliders, and Robin produced a few Bsa-type gearbox castings which would fit on the back of the Challenger engine and take the much better BSA gear clusters. Though the Albion gearbox is a bolt-on unit behind the Challenger engine such conversions are never as simple as “…well all they did was whip off the old box and bolt on a new one…” There are machining considerations to take care of, such as mounting holes for the studs which on the Challenger run right through the gearbox. In the courtyard of the Sammy Miller Museum as the late afternoon winter sunshine glistened off the polished alloy of this smart machine, Miller commented on the conversion by saying he couldn’t recall who was doing them but whoever it was “…certainly knew what they were doing and this must have been done in a machine shop…” Sammy and his right-hand man Bob Stanley had refurbished
this machine for its owner Simone Cunningham and Sammy had arranged for her to be on hand for our shoot so I could hear her side of the tale.
The Greeves we’re looking at is a 1967 250cc version of the Challenger Simone had bought a few years earlier when she’d mentioned to a moto-cross friend perhaps a lightweight bike would be the best idea for her to race in classic scrambling. Said friend knew of a 250 Greeves raced by a farmer down Devon way, the bike had seized in an event which caused a bit of damage and in the way of these things it was consigned to storage, actually a container, to await repair… repair which never happened, the old chap passed on and the bike was now being sold by his son.
Simone did the deal and came away with the bike but very quickly realised more specialist work was needed to recommission the Challenger to a rideable condition. “One of the first inklings this was something different was when the penny dropped about the gearbox, clearly it wasn’t a typical Greeves fitting,” she tells me, “further investigation, we took the primary cover off, and the primary drive wasn’t Greeves either so we brought in some help in the form of Bob Stanley at Sammy’s and he did the majority of the work as one of his last rebuilds before retiring.”
No point speculating
Anyone reading this who has ever had a motor seize in action will understand what sort of carnage can happen, or what will be found when the engine is stripped. In such cases there’s no point in pussyfooting around thinking ‘will it be this? Or will it be that?’ The bike broke, get it apart and see what’s what rather than speculating. In this instance the main damage was to the barrel liner which had cracked and there was no other option but to send it up to Nametab Engineering, have the liner removed, a new one dropped in and bored to take a new piston.
Job sorted at least as far as the barrel was concerned. Once the barrel was away thankfully the rest of the engine was relatively undamaged and it was a pretty normal rebuild, if there can be such a thing working on a motorcycle which has been used in scrambling and then stood for 20 or more years in a container.
Inside the crankcase sits an Alpha Bearings crankshaft which was stripped out to replace the big end while the plain little end in the con-rod got a new bronze bush which was reamed to size once the gudgeon pin was available. Inside the cases the main bearings were pitted after standing for so long and useful only as a door stop or something, once replaced the crank could sit back in place and assembly could begin.
Mixing and matching components is a difficult enough job when the parts are all from the same manufacturer, so fitting a BSA gearbox where an
Albion one was supposed to be required a bit of effort. The job was made slightly easier or perhaps more viable because BSA themselves used a semi-unit construction for their plunger A7 twins and instead of mounting the gearbox between engine plates they bolted it to the back of the engine on four mounting studs. Aha! Dead easy, that’s what Greeves did with the Albion box…
Are the mounting stud holes in the right place so the shell butts up correctly to the engine and allows the mainshaft to sit just so and ensure the primary chain line is as it should be? Having worked in the heart of the British industry in his Ariel days it is likely Sammy was aware of the mounting method and perhaps his cryptic comment of the conversion having been a tool-room job suggests the BSA stud holes would be nowhere near the Albion ones.
Apart from this difference in mounting holes the rest of the box is pure BSA and the benefits of a much sturdier transmission to cope with the Challenger’s extra power could only have helped the bike. There were some issues with the kickstart quadrant setting which needed some careful assembly but once this was done, the box in place then the primary drive, being mostly BSA or Bsatype, was reasonably easy to sort out from there.
Greeves had broken with their tradition for this version of the Challenger as it was available with Ceriani front forks rather than the ‘banana’ type though the cast aluminium frame still provided the basis for the bike. Work on this aspect of the Challenger meant checking it wasn’t cracked and replacing the steering head bearings up at the front bit, further back the rear of the BSA gearbox has a couple of mounting points and the original conversion had provided frame alterations for these. There was a slight issue with tyre selection as the swinging arm took what was for the Sixties a super-wide rear tyre but these days seems rather narrow and finding a suitable one took some net-working. The Italian Ceriani forks revolutionised the suspension scene when Sten Lundin was invited to develop them by the factory in the early Sixties. Suffice to say in a Greeves feature the forks became the new must-have units and ousted the previous favourites – Norton’s Roadholders. With parts still available the fork rebuild was straight forward as too were the wheels. The hubs were in decent condition even though the rims and spokes were not so good. So, cleaning up the hubs, fitting new bearings and rims before popping the tyres on sorted them all out.
Home-made silencer
Air boxes and filters had become popular on off-road bikes in the Sixties and we’re told fitting the ’box to this bike was interesting and involved many attempts, but eventually it was sorted and the new Amal Concentric carb breathes the finest of filtered air. Once the fuel and air mix has been burnt in the cylinder it needs to come out and the fashion in those days was an underslung silencer and exhaust pipe which was vulnerable to damage. It was actually rotten so useful only as a pattern and here Simone’s skills came in to play and she made the silencer herself. “I’d come along to do some adjustments in the workshop,” says the lady whose day job involves making sheet metal components on Second World War fighter aircraft restorations.
Naturally the mudguards didn’t survive the intervening years but these are available in the correct shape, a glass fibre tank needs care these days as the ethanol in modern fuel will delaminate the older resin and at best make the tank leak, at worst block up the carburettor with solidified gum. There are treatments available, however the careful out there tend to drain the tank as soon as possible. Looking at the seat I enquired as to the upholsterer and learned he’s a contact of Sammy’s and does a lot of work for him…