I believe it is 0.079 inches (1.8 mm) but it is possible i´m slighly off because my bike is a ´78. But thats what I set my new ones at and she runs like a top. I love my old bike, people stop me all the time to compliment the condition of my almost all original DT250. (only levers and have been upgraded to shorter ones because of hitting and breaking when riding aggresivly and oversized tires)