I now have two Jubilees- both apparently 1961 but quite different. My original blue bike still much like the 50's bikes: Saddle (now restored) still uses the twin rubber bush front mountings. The second (red) has been modified with front mudguard and rear light from a 70's Japanese bike- probably a Yamaha. The saddle hinges up towards the rear. This bike also lacks the "choke" air slide control present in the "earlier" model.
Tank Mountings:
Both bikes seem to have muddled tank mounts. The tank is mounted onto a rubber bush at the front, but the rear is bolted to the frame using a weld nut positioned on the underside of the frame lug. The bolt should be cushioned with rubber washers, but in my case the blue bike was fitted with a pile of grommets and petrol pipe, whilst the red had some large degraded rubber washers fixed on top of an old wheel bearing!
By pooling both bike parts I could assemble a set of the correct mountings for one bike, however rubber washers were all damaged, perished or absent so I bought new rubber washers from NOC.
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| From left to right (and bottom to top in position): Top hat rubber washer, steel collet, top flat washer cover washer and bolt/washer. The top hat washer fits at the bottom on top of the frame with the collet inside. The projection fits through the tank rear mounting eye with the flat washer on top and the cover washer on top of that |
The collet fits inside the top hat washer and prevents this from being crushed as the through bolt is tightened. The bolt could be screwed into the weld nut of the blue bike.
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| Tank rear mounting eyelet. Weld nut positioned under the hole in frame below |
In the red bike the weld nut on the frame lug had been drilled out to allow a through nut and bolt to be fitted anchoring the pile of wrong fittings that secured the tank in this bike. Since the weld nut had been enlarged a new bolt would be no help and as this is already a non standard bike I simply tapped through the frame weld nut to M10 and then fitted an M10 shoulder bolt cheaply available from Ebay.
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| New rubber washers as above and M10 shoulder bolt |
It was necessary to enlarge the holes in the rubber washers to accept the shoulder and as the shoulder in this bolt was slightly too long, I reduced the length of the shoulder by turning the shaft down to the width of the threaded section. This allowed the sbolt to fit lower, so that the shoulder just fitted on top of the frame when tightened. Since the M12 shoulder cannot pass through the M10 weld nut, it is not possible for it to compress the top hat washer and so the internal collet is no longer necessary.
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| Original bolt (right) and turned bolt (left) |
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| Weld nut tapped to M10 and top hat washer inserted below tank eyelet. The pic suggests that the holes don't align but in fact the tank can easily be pushed forward on the rubber bush to align the holes. |
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| Tank rear mounting |
Tank fixings in place.
Carburettor
Bike number one was fitted with the air control (choke) on the bars and the cable connecting this to the slide mechanism inside the carb. The second bike had no cable or control, the internal parts of the choke were missing and the cable entry on the carb top was sealed with insulating tape! I could restore the slide mechanism and cable plus control as all parts are available but this would be expensive. Furthermore the air slide is not particularly effective anyway and starting is usually done using the tickler. Its even possible that these later '61 bikes had no air slide fitted? In any event Amal sell a plug bolt to seal this cable hole suggesting that the air choke system isn't always fitted.
I bought the correct screwed plug from Burlen and also the clip that secures the top retaining ring. Sadly there was some problem with the plug supplied and it didn't fit the carb top. I therefore tapped the carb top to M6 and inserted a standard M6 bolt to blank off the hole. The clip was fitted using the new M6 bolt and the central screw.
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| Modified Carb top: Note throttle cable on left, central fitting screw and new bolt plug inserted into the unused choke cable hole. Screw and bolt used to secure retaining clip. |
Fuel Tap
Bike no 1 was fitted with a plunger type Ewarts tap which worked well. The more modern bike had a very stiff brass tap as shown.
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| Brass fuel tap, this position is actually "on" |
I don't know if this is an original tap but there were several issues with it. Firstly the tap positions were counter intuitive; the tap being in the "on" position when it was fitted across the outlet and "off" when in line. This is the opposite to the usual convention.
Secondly-if the fuel tap was left "on" without running the bike this lead to carburettor flooding and loss of fuel through the overflow. This suggests that the float valve in the carb may need attention as well.
New fuel taps are available from the NOC (although very expensive). Investigation showed that the tank body is threaded as 1/8 BSP and there are few petcocks of this size available in the UK, most bikes using a 1/4 BSP. However simpler taps are readily available from eBay and far cheaper! The tap below was purchased for just £2 from eBay.
This tap (which even comes with a top fuel filter and settling bowl) is threaded M10 1.25 and will not screw directly into the tank. Fortunately a 1/8BSP to M10 1.25 adapter is available from Venhill as a brake system build part for £5 and this works well to allow the new tap to be fitted.
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| Venhill 1/8bsp to M10 1.25 adapter |
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| Being a brake part its sized for a flared fitting internally but this can be easily drilled out a little wider |
The 1/8bsp section was drilled right through the fixture to 4mm (the diameter of the original tap pass through passage) and then enlarged internally to 6.6cm but to a very shallow depth (3mm) so it could be tapped to M7. This allowed the fuel filter that came with the tap to be screwed into the top of the adapter before this was screwed into the tank, and then the tap body could be screwed into the M10 socket in the base. Fibre washers were included above and below the adapter to provide a fuel-tight seal.
Carburettor Float valve
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| Carburettor viewed from float chamber (bottom), note tickler button centre, and fuel inlet banjo on right |
The fuel inlet banjo and intake filter were removed by unscrewing the small top bolt (left in pic above) to remove the banjo union. I knew that the PO had renovated this carb and replaced the filter only recently so I was surprised to find it already dirty. I guessed that this muck might be blocking the float valve which was therefore also removed and cleaned although no contamination was evident. The float needle had already been replaced with a Viton tip and the float was fitted correctly and showed no sigh of leaks.
However, removing the banjo (above) also showed that there was a fibre washer beneath the float valve housing seen in picture above to the right of the tickler button. This was apparently a metric sized washer that was a poor fit over the threaded spigot. In fact no washer is shown in this position in the Amal diagrams, and one is fitted there only to "later" carbs. In fact this position is used to adjust fuel height with shims so it seems that the use of a washer where none is usually needed would lead to a raised fuel level in the float chamber. This could also be the cause of the overflow I had suffered. Accordingly I removed this washer when the carb was reassembled. I will also include an in-line fuel filter since there does seem to be a problem with sediment coming through from this tank, however the tap filter, settling bowl and in-line filter should control this in future.
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| Clean fuel filter |
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| Float and needle reinstalled once needle housing has been replaced without the fibre washer |
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Banjo reinstalled using new fibre washer beneath retaining bolt.
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