Clas­sic Cob

From the shed

Old Bike Australasia - - CONTENTS -

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.

You can get in touch with Pete at... cob.smith@big­pond.com or call (02) 6553 9442 af­ter 7.00pm

RIGHT Drive side of John Ho­ran’s spe­cial. BE­LOW John Ho­ran with his BSA of many colours.

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