These carburetors (mfg. by Tillotson) are popular on all types of engines. 4 cycle and 2 cycle. They were the common fuel delivery system on many 2 stroke snowmobile and boat engines. Harley-Davidson had this model as standard equipment on Sportsters and Big Twins in 1967-1971. The KRTT, XR750 and XLR ran Tillotson carbs (single and dual) for all their race engines. I restored this one for the iron XR750. The motor had a version with no accelerator pump - but this model may aid in starting, and be a bit more practical. I'm rounding up the correct throttle(internal) control, correct handlebars and cable control. May as well do it right - like the factory did . . . This carb has a fuel atomizing "bomb-site" in the bore, and a unique 2-piece choke disc that spring loaded to relieve pressure upon a backfire. I also found this rare velocity stack.