Vintage british motorcycles such as Triumph, BSA and Norton use fuel valves with 1/4 inch BSP (British Standard Parallel) threads. These reproduction petcocks are made in the UK and feature all metal internals and a cleanable fuel filter. This replacement petcock will replace the leaky, hard to turn, worn out petcock on your vintage motorcycle and give you trouble-free performance. OEM part number is 83-2800, and was found on most Triumph 250, 500, 650 and 750 cc singles twins and triples from the 1950's through the early 1980's. Replacement for OEM # 83-2800 On the majority of British bikes this valve works on they will have a reserve valve on the left side of the tank and the main valve on the right side . Then the carb or carbs would have a dual banjo fitting so they are connected together at the bottom for a dual carb application or a dual banjo on a single carb . Then only the right valve is used until the reserve is needed and then you turn the left on to get the rest of the gas out of the tank . There will not be 3 positions on this style valve it is either ON or OFF.