Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126404
- .... c, < $.0 (Above) Paint makes the valve stem easy to locate in a hurry. (Below) Fins are cut away for easier access to spark plug. (Above) Tools. extra plugs and wire are carried on the downtube. (Below) The Can-Am was fitted with a lighter X·Dusor silencer/spark arrestor. 22 2 .55mm (stock) to 2.40mm. and the deck height" was raised slightly. from .052 inches to ,.060 inches. and made mo re - ccu r a te , decreasing the a extremely high compression ratio of the KTM power p lant. (T he deck height is increased by adding gaskets at the base of the cylinder. not at the head .) Surgery on some of the fins on both the cylinder head and the lower rear portion of the cylinder. itself, was done to give better access to the sparkplug and the carburetor. both d ifficult to get at on the stock machine. A hole was drilled in the top of the right vertical head fin near the front so the sparkplug wire could be tied away from the exhaust pipe. The sparkplug wire on this bike is much too long when it comes from the factory so it was cut to the right length and a waterproof Malcolm Smith plug cap was installed . The coil wires were safetied to th e coil with .080 inch stainless wire underneath protective rubber boots. This prevents the wires from comi ng off the coil , at the sam e time maintaining waterproofing. The coi l, itself, was ta ped firm ly to t he fram e, and weatherstripping was added to the top part of the frame a t the points where the gas tank rests to pad it. The Big V54 carb comes with a float designed to increase fuel capacity in the float bowl to help eliminate the fuel starvation problem experienced at high speed with earlier Bings. But with a #50 pilot jet this extra howl capacity causes a rich running condition on low end. and when the engi ne is stalled it allows fuel to dump directly -into the engine. To cure this problem , Dirt Factory put inthe old-style floats and switched to a #40 pilot jet. which still allows passage of enough fuel to start the engine when it is warm . Results of this method have been excellent, The original #175 main jet was replaced - with a #170 , and the needle jet was changed from #320 to #318. The stock needle is used in the center position. Other changes to the carburetor were removal of the choke (the Bing also has a tickler) and modification of the overflow tube in the float bowl , ' which ends flush with the bouom of the bowl and occasionally allows dirt or water into the carb o The original tube was removed . then replaced with one that extends below the bottom of th e bowl about one- quarter inch. A .piece of model airplane fuel lin e was fastened to this, and it extends down below the engine. All other overflow lines ~ere lengthened so gas couldn't pou r on the engine , th en bundled together out of the wa y. The idl e adjustment screw and air scr ew wer e safety -wired. and a hole was d rilled in the flange on the side of the carb so a sp a re main je t could be carried there.