Jims On-Bike Valve Spring Compressor Tool For Harley The innovative on bike valve spring compressor tool by Jims offers a breakthrough solution for Milwaukee Eight engines, eliminating the need to remove the cylinder head for valve seal replacements or valve spring upgrades. This patent-pending technology saves both time and money by allowing the work to be done with the cylinder head still mounted on the engine. Features: This patent pending tool dramatically saves time for any technician working on Milwaukee-Eight performance upgrades or service work Simply remove the rocker box covers and rocker arms, and install this unique compressor on the rocker arm shaft Once the cylinder is filled with compressed air, the technician can easily rotate the tool and compress the top collar of the valve spring exposing the keepers to remove the top collar, valve spring, and seal Made in the USA