Let there be light, light weight that is! This is becoming a theme for PUB, whether in her classic bikes or anything new (with that desirable button). The latter were on show at Motorcycle Live, but left her with too many options
Something of a shadow is cast over the season of good cheer, with the recent death of Bruce MainSmith that will have been widely reported by now. Not surprisingly Bruce was an acquaintance of PUB, since he had been a past Chairman and Vice President of the VOC. He then graduated from writing club articles to being a staffman on Motor Cycling, and was a good enough rider to be included in Velocette’s 24 hour record breaking team at Montlhéry. Subsequently he published various books, including a series of Vintage Road Tests by Titch Allen, and manual photocopies that are still available (from the National Motorcycle Museum). For a time he took his stall to various shows, so many readers may have seen or met him.
Then more bad news arrived for Vincent enthusiasts, with the news that Patrick Godet has passed away unexpectedly. PUB had known Patrick for many years, having attending an early rally organised by him in France. Patrick dedicated himself to the marque with such good effect that a Godet-Egli is now a very exclusive machine with a worldwide reputation. His racing efforts have put the Vincent name back into contention at events such as the Classic Manx, with both Egli-Vincents in later classes, but also replica Grey Flashes eligible for earlier classes – a welcome addition to the variety of classic racing. It may be no more.
Closer to home the focus – probably more accurately described as out of focus – for PUB’s spanners this month was a vintage AJS, which is still not properly on the road. This era of AJS is incredibly light, and an ohv model should rattle along a little faster than her much loved but slow sidevalve HRD. Having done various things since its acquisition, including replacing a duff magneto from ‘stock’ (since repaired and put on the shelf as the spare), relocating footrests where they should be (involving making engine plates), and fitting up a kickstart albeit bodged with parts apparently from an earlier model, the bike needed a test ride. It did not start, and soon both the kickstart and PUB’s hip began to feel unhappy, so a gentle bump was used on a nearby slope. The bike then started up easily enough, but throttle response was horrible, and shortly all came to a halt as the primary chain escaped. There is no way to avoid the last catastrophe being PUB’s own fault, because she was the last person to fit it, and the spring link had departed through ill or unfinished fitting – oops.
The chain was an easy fix, but less so the throttle response, although the issues were clear enough. For a start, previous owner (a sprinter) had discarded the Binks ‘2-jet’ air slide entirely, and the throttle control was a period ‘straight-pull’ type with horrific backlash. Dismantling it proved to be fairly involved, because it required the twistgrip to be slid off the bars, but as inverted levers were the vogue in 1927 that in turn required the front brake lever disconnecting and extracting first!
These straight-pull twistgrips utilise a longitudinal slot, sometimes integral with the bars but in this case part of the slipon inner, and a scroll machined into the outer, twisting, part of the twistgrip. As the
grip is twisted the alignment between the two slots moves along the bar, taking the cable end with it. Previous owner took that description a bit too literally, for it was assembled with just the cable nipple engaging the slots, notwithstanding it being considerably smaller than either – hence all the backlash. PUB surmised that there ought to be a suitably close fitting ‘shuttle’, and that probably not integral with the cable but able to accept a conventional nipple. So she set to to make one.
However, that required a pattern, which she did not have. This was solved with a bit of blu-tack / plasticine, pushed up inside the assembled grip whilst it was off the handlebar. The imprint left indicated not only the widths required (which could have been measured) but also the angle between them. A piece cut from some strip steel was then filed up to this shape, and drilled for a cable nipple. Naturally it did not work first time, or second, or third…
The inner sleeve is made of thin metal, so the shuttle has to be similarly thin in part, and also similarly curved to follow the 1” bars. The thicker part engaging the scroll also has to be matched in its width and angle before a smooth action (or at first any action) is obtained. It quickly became apparent that the fewest relevant bits should be assembled on the bar until they worked alone, before trying more and eventually the whole thing plus cable. Even that was fiddly, and PUB suspects that a short length of slightly undersize bar might be a useful aid, the assembled grip then being slid off the tool onto the handlebar. But PUB has never been good at making special tools, and so condemns herself to perpetually do things the hard way. Perhaps PhD stands for Phenomenally Dumb?
Eventually, however, it was done, and the throttle could be operated with fairly minimal backlash. The makers actually added a circumferential friction spring at one end, but PUB considered omitting it, as there seemed to be more than enough. Friction and backlash are the reasons the scroll type of twistgrip fell out of favour, to be replaced by the more familiar drum type which operates very freely, although it does flex the cable.
The grip has now fallen out of favour with PUB too. Before she had even replaced the front brake lever she realised how much fuss a throttle cable replacement would be. Since both of her pre-1930 bikes already use simple lever throttles, she decided to discard the twistgrip, and use instead the twin levers that it also came fitted with. So all that work was for nothing – PhD! Those twin levers had been repurposed for advance / retard and valve lifter (the latter very strange, and difficult to use), but she had already fitted a more conventional valve lifter lever. Looking out a single, left bar, lever for the advance retard freed the twin levers for a conventional throttle and air configuration. Or it would if the carb had an air-slide.
Fortunately the air slide is not complicated, being basically a cylinder (earlier models were ‘D’ shaped), but drilled and slotted for a cable, and with a cutaway flat on the bottom end. That much can be seen in Radco’s ‘The Vintage Motorcyclist’s Workshop’ (a strongly recommended tome for novice and expert alike), but not any dimensions and PUB had no pattern, so there was a certain amount of guesswork involved. The slotting was opened wider with a Dremel, as PUB does not have much success with the old advice to fit two hacksaw blades side by side for a wider slot than a single one produces.
Meanwhile B44 ‘Clever’ Clive took one look at the well-worn throttle slide and offered to make a new one. Bad move by Clive. A couple of tries at making a blank to establish the requisite diameter only proved
that the bore of the carb was too badly worn, and experience has shown that a new cylindrical slide in a worn, barrel shaped body is worse than using the original badly worn slide. At least a worn closed slide seals marginally well against the matching worn bore when the engine sucks but an ill-fitting new one will not. The solution was to bore the carburettor body back to true again, which Clive bravely took on.
The Binks 2-jet does not use a needle, and therefore, it was reasoned, the new bore did not have to be exactly concentric with the old. In fact since around 10 thous of wear was all concentrated at the engine side, a boring operation centred 4 or 5 thous offset in the same direction would produce a clean bore with the minimum metal removal – and Clive was the man to carry out such a delicate operation. It may not be very obvious in the photograph, but he produced a perfect job, and then a new slide to fit.
Unfortunately, in the process of removing the jets to facilitate Clive’s work, the main jet broke – isn’t that always the way? This proved to be because it was not original, but comprised an adapter to utilise Amal pilot type jets (in larger flow size than normal pilots). That meant a 5BA bore up inside a 2BA thread, and that only leaves around 20 thous of metal, which broke rather than undo. Fortunately the remainder did not prove hard to remove.
Rather than replicating the adapter, PUB decided to make a couple of new jets as original, which would be more robust. The length was copied from the broken adapter, as was the drilling of one item, whilst the second was drilled somewhat smaller in case number one proves to be too rich (in the case of weak a jet can be drilled larger, although it is normally bad practice when jets are available). Radco’s book was again invaluable, for it contains jet recommendations for Binks, together with cross references to Amal jets and also drilling sizes.
Does it all work now? Well, who knows, for PUB has fallen into the trap elucidated by Editor Frank an issue or two ago, of describing in the magazine work still in progress. Readers will be told, or maybe will never be told, as there are just too
many things vying for attention in (and out of) the garage / shed.
The current and neglected modern hack (with electric leg) is getting tired as it approaches 100,000 miles, so PUB keeps an eye open for a replacement, be it a lower mileage example, a different oldish bike, or something completely new. The motorcycle show is the place to look for the latter. Motorcycle Live, however, tends to be based around the big, powerful, and fast stuff that obviously appeals to the younger, stronger, and usually male riders. If that is you then the following will be of little interest, because it homes in on the lighter and less powerful machinery that some mature motorcyclists are now looking for (guess who).
In recent years this has actually become a more fruitful area of interest. The 300400cc category that has been mentioned before continues to be offered by many manufacturers (Kawasaki Ninja 400, Yamaha MT-03, Honda CB300R, BMW G310R, KTM 390), except for Suzuki. Chinese 400cc air-cooled ‘Honda copy’ engined retro styled machines also remain available, with Herald having added one to their range, with an engine similar to (but not the same as) that of the more familiar MASH and the new JAWA 350ohc (neither seen at the NEC). The JAWA appears to be so named for historical reasons, as it is actually 397cc like the others. However, an additional bike shown by Herald was their proposed 450cc watercooled 43bhp ‘Brute’ model, which they claim is British designed and built. If that is true and it comes to pass it would be a welcome development.
Bikes also hailing, at least in part, from China, but not based on the Honda clone, were those on the Benelli stand, and in particular the new Leoncino 500cc (Lion cub). It uses the same basic 4-valve dohc engine as the TRK 502 that has been around for some time. Unusually nowadays, this is stated to be a 360 degree twin, with a balance shaft, which offers 47bhp from a bike of dry weight 186kg (196kg wet?), and with a reasonable 785mm seat height (31 inches). The Benelli stand also showed an example of their proposed 373cc single cylinder Imperiale, but with few details except a power of 20.7bhp (however Morini Alan did find the seat height OK). Apparently it is intended as a 350cc Bullet competitor, but surely a new machine ought to try to outperform the competition, and in this country that will probably be the 500cc model and 27bhp anyway?
PUB did not see a repeat of last year’s A2 offerings from either Ducati (the 400cc Sixty two, although it appears to still be available) or Triumph (who seem to have replaced theirs with a restricted 900cc Street Twin). But as most RC readers have full licences the full fat 800cc Ducati Scrambler is probably of more interest anyway, and comes in at a reasonable
189kg wet. The newest 900cc Street Twin is rather heavier at 198kg dry (around 210kg wet), OK for most people but a bit much for PUB (it is the same as the quoted weight of a Vincent, although that may be dry weight). On the other hand its 750mm seat height (29.5 inches) is quite acceptable. Power quoted is 54bhp, which may seem a bit low, but the power and torque curves show that it is tuned for its bottom end, which should make for relaxed riding, especially at the famed 55mph, or even street legal speeds. For many people the 765cc Street Triple may have more appeal with its 112bhp, a svelte 168kg dry weight (approximately 185kg wet as it has a 17.5 litre tank), but a rather higher seat at 810mm (32 inches), but it is in no way ‘retro’.
The Royal Enfield twins seem now to be here for real, and likely to have a significant appeal. Like the Triumph, they feature a 270 degree crank and 270/540 degree firing, an idea long ago propounded by Phil Irving but ignored until Yamaha introduced ‘cross plane’ cranks. Sadly its adoption now is probably as much to do with aping the sound of a Harley than with the desirable mechanical benefits (the pistons desirably do not come to a halt at the same time). 47bhp may not be much, but it is actually slightly more than the PUB Vincent, and enough for many, although six speeds may prove to be one more than was necessary. Weight is 200kg (plus or minus 2kg according to model) plus fuel, so significantly higher than necessary for A2 licence power to weight ratio (not less than 175kg for a full 47bhp). This is OK for many older riders, to whom the ‘traditional’ looking Enfields may prove very attractive – but PUB has her heart set on lighter still.
Of similar capacity are the new Norton Atlas 650 twins: the Nomad roadster and Ranger with a bash plate. A 270 degree
crank is again adopted, making this a very popular configuration. The Norton offers 84bhp (enough, surely for those with not so young reaction times) in a 178kg dry weight package that sounds quite attractive (190kg wet). Slightly oddly, to PUB’s eye, they have made a polished feature of the high up clutch cover, but the styling mostly seemed pretty good. ‘Mostly’ because the quite pretty seat looked very high mounted (although nicely flat, rather than the common stepped layout), and this is reflected in the quoted 824mm seat height (32.5 inches) – nice for the taller people out there, but Norton would do well to investigate a low seat option as do so many other manufacturers.
Their front mudguard follows the execrable modern fashion of not guarding against any mud, and needs to be a foot longer – but they ‘are all like that sir’, and the Norton may be easier to alter than many. The Atlas looks to be a sound and modern design, upon which the Norton revival might make some further progress, so wish them luck (or even buy one).
Not so long ago there was very little in the middleweight category between the modern light and high power race replicas and behemoth touring and adventure models, and even less with a traditional look. Now there are various retros and middleweights everywhere too if 180200kg qualifies, but no real shortage even at lower weights than that. PUB is spoiled for choice, Japanese, European, Chinese, performance level, price, a new bike or something older and eligible for VMCC runs. Decisions, decisions. So spoiled for choice that her head spins and procrastination wins the day.
Happy New Year!
Twistgrip outer sleeve, within which can be seen the helical scroll
The extender fitted between cable and adjuster. A little black tape can make it a bit less obvious (and slightly more secure)
Vintage Binks carburettor body in B44 Clive’s lathe, after boring true and parallel again. A fine job, but this is not a task for the faint hearted, or beginners
When the front brake lever had to be dismantled to release the twistgrip it was noted that its adjuster was at its limit. Rather than shortening by soldering the nipple to old and oily wire, this outer extender was turned and slotted
The lower lump of plasticine has been pressed into the operative twistgrip grooves to produce a rough pattern. Copying this in steel produced the upper shuttle, which has been drilled to accept an ordinary throttle cable nipple
Above: Component parts of the straight pull twistgrip: inner sleeve with cable abutment, outer sleeve, within which is machined a scroll, outer end clamp and its mating circumferential spring
Herald is the latest to offer a 400cc classically styled model, based on a Honda copy. However, this engine is not exactly the same as that of the MASH or JAWA, and is sourced elsewhere
The main jet, on the left, broke on removal (which was necessary to clear the carburettor for boring). It turned out to be an adapter, double threaded inside its 2BA to accept a 5BA Amal pilot jet. The wall thickness left makes the adapter very fragile, so the replacement (right) was made more like an original Binks item, even to having square rather than hexagon head)
The AJS Binks carburettor is unusual in screwing into the head, with a locknut. Here it is seen with newly made throttle and air slides, and a new, long, main jet (the pilot jet is short and original)
Herald also showed this Brute model, of 450cc, and claimed to produce a healthy 43bhp. It claims to be ‘engineered and built from the ground up in United Kingdom’, but is not currently available
As well as the new 47bhp 500cc Leoncino 360 degree twin, Benelli were showing (but not advertising the availability of) this 373cc Imperiale single. With a claimed 20.7bhp it is not likely to set the world alight
The new Norton Atlas is offered as ‘Nomad’ for the road, and this ‘Ranger’ for slightly less ideal tarmac, with a bit more ground clearance and a bashplate
The basic Street Twin is also the lightest of the variants at 198kg dry – an improvement over the older Hinckley Bonnevilles. Power is apparently down at 54bhp, but the fat torque curve says it may perform better at real world speeds
Honda have re-introduced their Cub, a Classic if there ever was one. This time, however, it has 125cc, rather than the 50/70/90cc of its predecessors
Hot new introduction at Motorcycle Live was the new Norton 650cc Atlas – this is the ‘Nomad’ version
Above: Modern technology at Motorcycle Live may not be RC ‘core business’, but BMW’s ‘shift cam’ cylinder head is topical and interesting anyway. The inlet camshaft has four lobes, one lumpy pair for high power and a second gentler pair for docile and economical running. The changeover is reported to happen in milliseconds (as it needs to, because one whole engine revolution lasts less than 8 milliseconds at the 7750rpm maximum power speed). The two inlet valves are also given different cam timings, which is claimed to improve swirl and combustion. The lower camshaft has just two lobes, one for each exhaust valve. A pin visible within the exhaust cam is an automatic, centrifugally released, decompressor, used by BMW (and others) to ease the initial load on starter motors. The boxer has 2 such heads, 12 cams on 4 shafts operating 8 valves. Contrast that with PUB’s Victorian voiturette that has a single mechanically operated valve (plus an automatic one) operated by one cam (however the BMW is ten times faster)