I'd guess the first 'S' types were built as a batch (of ???) so there might not have been any Fastbacks within the first 50.
A good point, but considering that they were trying to get motorcycles built -- and a completely new model at that coming into production -- whilst looking at a gummint-mandated factory closure within a 2-3 month window, there's a good chance that anything and everything that they had a complete production "kit" for would have been greased up and pushed through the assembly line. I'd love to know for sure but it would take a research-look through the production data to find that details.
I don't know if all R types had the 20M3 engine or not, but all the R types seen so far have been 20M3.
According to Roy Bacon's data, the Fastback didn't get the 20M3S engine until "Sept. 1969, 133668".
Again, it would take a detailed study of production records (and I'm not even sure that the data from the time shows the engine type) but surviving data, old adverts, and individual motorcycles still in existence all point to the likelihood that the "R" models were entirely based on the 20M engine. I'm a bit surprised that Fastbacks didn't get the 20M3S engine until about 2500 engine numbers after the intro of the "S" model, but having seen Fastbacks on my Norton dealer's show floor in North Carolina in the summer of 1969 with the 20M3 engine, it fits into my experience. (Of course, Berliner in the US were infamous for pushing "last year's models" as current production so who knows the mix. Also, in this little backwoods dealer in the pine trees of central NC, there were two of Fastbacks with the silver paint with the translucent burgundy "shadow spray" -- which Mr. Bacon lists as "rare", it was all Wild West. BTW, dealers were told to push the Fastbacks to buyers and get them out the door. I had to fight my way past the 20M3 engines to buy an "S" as my first Norton.)
Also, I've heard it said that the 20M3S engine was the "first Wolverhampton engine and all of the series-production engines were built at Wolverhampton", which appears correct in general if not entirely in detail, at the same time that Plumstead Road was making as many 20M3 engines as possible to keep production numbers high, there would have been intense pressure to mix whatever could be built. The company's survival was entirely dependent of getting motorcycles into retail customers' hands as is demonstrated by RDPs unprecedented move to book the inside-cover of the US "Cycle" and "Cycle World" magazines as the springboard for the inception of the "Norton Girls" advert series.
How? No, although I believe it was Bob Trigg's design.
Indeed. Berliner was screaming for a competitor to the Triumph Bonneville and the Harley Sportster due to what Mike Jackson describes as "intense sales resistance" towards the Fastback in the US. As Berliner liked to do, they went out and bought a couple of Sportster fuel tanks as well as some US custom aftermarket "peanut tanks" and shipped them to the UK. At the time, Triggy (along with Bernard Hooper and John Favill) were "commuting" from the Midlands to London for the workweeks and the train rides gave them opportunity to free think. It was established that the new "Sports" model with US street-scrambler styling would have lots of chrome plate and brightwork (many of these components found their way onto the "R" model) but the issue of tank and seat styling was ambiguous. They tried the US mini-tanks on a styling mockup -- Tony Denniss (production design engineer at AMC/Wolverhampton/Rotary project) described it as looking like a camel's hump on a ferret -- which appeared to be a dead end.
With a feeling that they were treading water, the usual corporate solution to problems -- meetings and discussions -- kicked in with no real progress being apparent.
Triggy looked back and said "lateral thinking". A big part of it all was getting rid of the 1950s-comic book-rocket ship-look seat and Fastback tail fin. Easy - a flat Bonneville-style seat, a chromed rear mudguard, and a BSA style taillamp and lamp housing and number plate bracket. But what for a fuel tank??? Discussions, discussions. So after a late-evening train ride to Birmingham on a Friday night, Bob got up on Saturday morning, went to the DIY store and bought a block of plastic foam, and took it to the picnic table in his back garden. Using his wife's electric carving knife, and scaling the rear of the tank to the width of the Fastback's seat-ears, he free-handed a sculpture of what he thought the new sport tank should look like. He brought the carved block into the design shop at Woowich on Monday AM and within a few hours, they had established the tunnel under the foam block for the Commando backbone tube, slightly shortened and rounded the front end to match the steering head dimensions and allow for full steering angle fork clearance.
Then woth the tank sitting on mockup bike, they put on a thin coat of filler, sanded it, and sprayed a quick coat of paint. Then, with a couple of Polaroid photos, Triggy caught a cab on Tuesday evening to Love Lane (Manganese Bronze head office) in time to catch RDP for a discussion on the proposed new model (RDP liked to discuss things like this after the end of the work day -- I don't know how he ever found time to go home). By the time that Triggy had left there that evening, they had agreed on the overall stying scheme for the "S" model. A new model was designed and approved in two working days. There followed the hard work of matching tank to seat, getting a glassfibre moulder to tool up for production of the tank and taillamp housing, final design approval of the exhaust, etc. but they were on their way to the first sister model to the Fastback.
That's the story of how the "S" - "R" - "Roadster" tank -- the longest used Commando fuel tank in production history -- came into being. Yep, Bob Trigg.
