The new HPI Rotostart unit will fit directly onto your Force motor, nothing additional needed. It merely bolts right on, and works like a charm.

For Picco motors the process is just as simple but with one added step. The Rotostart fits the Picco 26 and the Picco Sport with an added adapter piece. #39298 You can also use the plastic ones, or any 12mm x 5.5mm nut or spacer will do.
Examine the process below to learn more.

Follow the instructions to assemble the rotostart backplate.
Remove your old pullstart backplate. If you have a Picco take care not to lose the spring shown in picture.

For the Picco motor you will also need the adapter shown. This adapter is an OFNA hex drive nut. The part number for the hex drive nut is #39298

You only need the adapter for Picco motors

Grease the Rotostart backplate chamber lightly. Push the Hex Nut, flange end first, into the Rotostart backplate chamber. It will slide in effortlessly and will keep your one-way bearing from throwing out.

Make sure you reinstall the spring into the new backplate. Bolt the rotostart backplate onto your motor and you are ready to go. You will need to purchase a battery for the Rotostart gun.

Insert the dogbone end into the slotted hole in the housing, press the red button, and start up in a hurry.