The Mikuni genuine viton tip needle valve assemblies are the best replacement parts for your leaking carburetor.  The 786-27001 viton tip needle valve assemblies fit the HSR42, HSR45, and HSR48 carburetors.  The set includes a viton tip needle, press in type needle valve seat, and sealing o-ring.  Available in various sizes from #2.3 to #4.5 in order to match up to the fuel flow characteristics of your engine. 


Standard size for HSR42 and HSR45 is #4.2.  Standard size for HSR48 is 4.5.


These needle valve assemblies include the sealing o-ring, no one else includes the sealing o-rings!


Please feel free to contact us with any additional questions or requests, we are available by direct line, IM, or email. We are available for tuning and setup questions as well as continuing product support after the sale.