Only occasionally does a cool motorcycle engine come along. Usually it's installed from something completely unusual, by someone very creative. Bo Hare in this case

It’s in a 1930 Peugeot P50T oval boardtrack racer. Modern scale version of WW1 period Gnome&Rhone overhead valve 9 cylinder radial aircraft engine. Methanol premix fuel. Glowplug ignition. 100 cc, 7hp 7000rpm.

There are double d-cells in the fire extinguisher case giving 22,000mah for powering up the plugs

Found on https://www.facebook.com/BikeShedMotorcycleClub/photos/a.982441528446099.1073742635.312531012103824/982441921779393/?type=1

https://www.facebook.com/bo.hare.79

Radial engine video of Bo Hare 

You can read about him in Classic and Sports Car, April 2015 page 185