For a KLR650 throttle body (TB) a modify used BMW R1200 TB with its corresponding throttle position sensor (TPS) will be used. A single throttle cable is required to open the BMW throttle blade. The BMW TB is easy to fit within the confined space of the original 40 mm CV carburetor.
Throttle Body Dimensions
With its length of 108 mm the BMW TB is only 8 mm longer than the KLR’s CV carburetor. Air box side is 54mm and engine side is 45 mm. The throttle blade is 50 mm. To use the BMW throttle body a slightly larger adapter to the cylinder head is required. The adapter was fabricated from 6061 Aluminum and use a silicon hose to connect the throttle body to the adapter. The throttle body has a set location for a fuel injector just after the throttle blade on the cylinder head side. Although the BMW idle control valve will not be used it was decided to keep it in place. This action require less modifications.
Fitting a new Fuel Injector
The standard BMW fuel injector does not supply enough fuel for the KLR650 fuel injection project. The 550 cc Denso fuel injector chosen for the project required the throttle body to be slightly modified at the injector inlet side. The modification required a high degree of precision, is simple and was fairly easy to complete.
Why the BMW TB was Chosen?
The BMW TB was chosen because it allows the throttle blade to be opened progressively. Its taper design allows for the increase of airspeed and in its unmodified state it will support 425 CFM when connected to a fully ported KLR cylinder head.