Carburetor Rebuild Kit for Tillotson RK-21HU Aftermarket Carburetor Rebuild Kit for Tillotson Replace Tillotson RK-21HU Use DG-4HU if you need a Gasket & Diaphragm Kit For Tecumseh two stroke engine models with specified Tillotson carburetors Order by 5.00 PM, ship at next day with USPS first class mail.