New carbs for classic bikes
JRC Engineering of California acquired the inventory and customer list of Triumph in the USA after the company folded in 1982 and has been making and selling parts for classic British motorcycles since then. Their latest development is an advanced carburettor kit...
JRC has developed an advanced carburettor kit specifically designed to replace the original Amal carbs fitted to most Britbikes up to the early 1980s, and to overcome the problem of ethanol in modern fuels. These carbs are now available from Brill Bike Bits in the UK.
The JRC unit is designed to replace the Amal Concentric Mk1, Mk2 and Monobloc carbs, so covers a vast range of classic British bikes from the 1950s to the early 1980s. The problems with ethanol in modern fuels are well known among enthusiasts. Ethanol, like any other form of alcohol, attracts or retains water and tends to dissolve plastic fuel lines, fibreglass tanks, varnish and rust on steel and corrosion on aluminium. The resulting sludge settles at the bottom of the tank until it is dragged through the system into the engine, clogging filters and gumming up the carburettor.
Among the features of the JRC carburettor are its use of modern alloys designed to resist this corrosive action and a flat, hard chrome-plated slide, which gives a smoother action than the original round-section design. The JRC unit also has a ‘fuel enrichment device’ rather than a conventional choke, which provides better cold starting. There is also a cable conversion kit, which allows the cold start device to be operated from the handlebars.
The JRC carb comes in three throat sizes; 26, 30 and 32mm. The 26mm and 30mm carbs are available in kit form at £120 including VAT and comprise the JRC carburettor, fitting instruction, fuel filter, air filter, throttle cable and a selection of jets to allow tuning for specific installations. All parts of the kit are also available separately, with the 26 and 30mm carburettors coming in at £84 including VAT, while the 32mm size costs £103.20 and is currently only available as a separate item.
Ken Drinkwater, founder of Brill Bike Parts, is a mechanical engineer by background and a lifelong British bike enthusiast. He discovered the JRC unit when he needed to replace the carburettor on his own BSA A7 Shooting Star 500cc twin. ‘Given the higher ethanol content in American fuels, I was impressed by the track record of JRC Engineering and knew that their design would work at least as well over here.
‘I have been selling the carbs to enthusiasts who, I think it is fair to say, all find their bikes run more smoothly and start more easily. In fact, some have even been fitted in lawn-mowers and, in one case, a Messerschmitt bubble car!’
Ken is happy to offer advice if you’re unsure whether the JRC carb is suitable for your classic.
Originally appeared in RealClassic magazine May 2012
