Sunday, March 09, 2008
I've been working on the 1925 Sunbeam Longstroke, amending the faults which the DPO (Demented Prior Owner - a fabulous term) had foisted on the bike in the name of expediency, or sheer laziness. There are a few simple rules I follow when bringing a bike into at least 'period correctness'; no chrome on a pre-1930 machine, no plastic anything (zip ties, electrical connectors, etc), no materials or hardware which wasn't available at the time. Following these rules, if the exact part isn't available, the bike will at least look as it might have in its heyday, without glaring anachronsims. The Sunbeam had many examples of each of these faults, plus a few issues having to do with age and neglect. Top photo shows the engine bay 'as delivered'.
One footrest rubber assembly was missing entirely, while the remaining one was a built-up affair similar to Broughs and pre-'52 Nortons. I had nothing like this in my stock, so I found a pair of very worn and oxidized rubbers from a bike found in the SoCal desert. A little hacksaw work, finished off with a file and wire brush, plus a few large and oxidized washers (one of which wasn't black enough, so I coated it with grease and applied my torch until it was red hot), and suddenly both footrests had passably worn, and period-looking rubber, in keeping with the patina on the rest of the machine.
The rubber tubes which take up vibration on the solid fuel and oil lines were all perished, so I cut new ones, and removed the logo on the tubing with lacquer thinner and a rag, thus giving plain black rubber. My favorite method of securing Vintage tubing is small-gauge copper wire, which is tightly wound, the ends twisted tight, then soldered on (shown in the photos). I copied this technique from my '28 Sunbeam, and it sends a message that the owner cares. Jubilee clips (otherwise known as hose clamps) were actually invented in 1921 in England by L Robinson & Co, and thus are period fittings for any post-21 machine, but I prefer the look of wound wire on my oil and petrol lines. The top photo shows that early Vincents weren't the only 'plumbers nightmare'! The 'Beam has no less than SIX oil lines and one petrol line; on a machine with Total Loss oiling. This is actually a very sophisticated oiling system, bringing lubricant exactly where it is needed; it represents the pinnacle of this type of oiling on a sporting motorcycle, before fully recirculating systems became the norm just a few years later (my '28 'Beam has a proper oil pump).
The Amal (incorrect) carb needed a stronger spring, as the throttle lever wasn't returning quickly enough (lots of lag on the rev-down - not good on a machine with more engine braking than wheel braking), and I found the slide spring to be the small diameter type from the choke slide rather than the larger, correct type. I'll replace the Amal carb with an Amac when I find the right size on ebay or at an autojumble... but the push-pull petrol tap will go away tomorrow.
The clutch was slipping, so I tightened the single conical spring which holds the clutch together. This was a good time to examine the corks of the clutch (nearly new!), and glue one of the clutch stop corks into its recess (these stop the clutch rotating during a shift; as the clutch pushrod raises the outer clutch plate, it is bumps against these corks and frees the plates. Apparently Sunbeams don't shift as well without the stops, although my '28 doesn't have them, and I've never had any trouble with shifting). The DPO had used Allen screws to hold the primary and timing cover, so I rummaged through my drawers to find enough slotted cheesehead screws to replace them, adding oil to the primary case for good measure.
I also cut off the zip-ties and replaced them with friction tape - which is very unobtrusive and wears well. My '25 blown Zenith had 70-year-old friction tape on every joint, on the handlebars, footrests, around cables, etc, and it had all aged beautifully. New friction tape looks pretty much the same - matte and soft, timeless (let's hope that's the only poem I write about the subject).
Bottom photo shows the results on the tubing and cables; the flash from my camera found two more, hidden zip ties - aha!