PROX 99101-357 Keihin Hex Main Jet 160 XR400R

The Pro X 99101-357 Keihin Hex Main Jet #160 is an aftermarket carburetor jet designed for Honda XR400R motorcycles produced between 1996 and 2004. Main jets control fuel flow at wide-open throttle, and selecting the right size is essential for maintaining proper air-fuel ratios under varying conditions. A #160 jet delivers a specific fuel volume calibrated for certain combinations of altitude, ambient temperature, and engine tune — riders commonly swap main jets when moving between elevations or after making performance modifications such as exhaust or intake changes.

This Pro X jet is machined to replicate the dimensions and flow characteristics of the OEM Keihin 99101-357 series hex main jets. The hex head design allows for straightforward installation and removal using a standard wrench or socket, without requiring specialized carburetor tools. As an aftermarket part, it provides a cost-effective alternative to factory Keihin jets while maintaining the fitment and metering accuracy needed for reliable engine performance. Note that this product cannot be sold to residents of California due to state emissions regulations governing carburetor modifications.