These were made using reel type lawn mower engines. The greatest thing was building a foot operated clutch ( like an old Harleys heel/toe clutch using a jackshaft to go from belt to chain drive with a roller skate wheel spring loaded to tighten the V belt and thus engage the drivetrain. Rev up the RPMs and pop a wheelie or stand and burn some serious rubber!. A much safer but less intense clutch was later designed using a handlebar brake lever. Engines were from 1 1/2 hourse to 4 horse. All exhaust was hand made from scrap tubing. The springer forks were scratchbuilt using pieces from bicycle forks, scrap tubing, flat and square steel, and springs for screen doors. motor mount was 1/4 inch plate steel. fake frame mounted gas tank was a pop riveted Clorox bleach bottle with a speaker inside. Portable transistor radio was installed in a fake oil bag under the seat. Brakes were scary and were either front or rear centerpulls. I recall one friend who had a combination of compression and Fred Flinstone brakes. Not Reccomended!