Classic Cob
From the shed
So often owners of various motorcycles have had creative ideas, but not the talent or time to implement those modifications or changes which would result in a practical machine that was operational and reliable. At the July Lowood Swap recently I saw a machine arrive which initially did not attract my attention, but when later walking past I noticed some rather unusual features. I then got talking to the owner, John Horan, a Fitter and Welder from Toowoomba. He tells me that he has over the years restored BSA machines; two M20s, a M21 and a B31. Other projects he will undertake with parts that he has will be B31 and B33s. However the machine he rode to the swap is unique. It has a B31 rigid frame and gearbox, an M20 bottom end and that is about where the conventional machine parts finish. There is a Harley-Davidson Evolution Sportster barrel which came from a local rubbish tip. He has machined a one-inch thick plate under the barrel so as to give the barrel the correct length using the M20 conrod, and the barrel was bored to 82 mm to take the M20 piston. However the head, also from the same model Harley had to be purchased via the Internet from USA. Lubrication to the rocker spindles is provided by an oil feed line running from the return side. Harley-Davidson pushrod tubes were used but new pushrods were made with some modification to align these with the rockers. Also acquired from the local tip was a 21 front and 19 inch rear wheel thought to be from a CRF Honda, although he did have to purchase the discs. To complete the brake assembly John was able to purchase Chinese-made brake calliper, hose and reservoir on the internet, and that assembly cost him some $40. Some magneto problems were experienced so he used a distributor from an Indian manufactured Royal Enfield and removed the points so as to install a Pazon electronic ignition. This fitted straight into the timing cover with an adaptor plate that he made. Seeing as John had not long had a knee reconstruction he decided that some caution was required. A starter motor from a Holden Barina is installed on top of the gearbox which then drives a Harley-Davidson ring gear. This ring gear has been welded onto a late model Royal Enfield clutch which is what he uses on his BSA gearboxes. He tells me that these are readily available at $70 for a complete clutch assembly, and he machines the gearbox adaptor to take this clutch. A further modification in this area is to make the primary chain a duplex one using sprockets obtained from a local bearing service. However that’s not all. The alternator from a Kubota tractor was fitted and this is mounted at the front of the engine and is driven by a pulley belt from the drive side of the crankshaft. Other components are M20 front and back guards, a rear chain guard as well as the inner and outer primary chaincase he made himself, and a Royal Enfield seat with a BSA Bantam petrol tank. The front fork assembly is from a Suzuki and was not located at the local tip but purchased at a swap meet. To date this machine has not given any trouble in approximately 4,000km it has travelled. It has at one time achieved a top speed of just on 140 km/h. In my opinion this machine was not only practical but it gave me the impression it was well engineered.