Vintage doodlebug engine upgrade

[Yukoncornelius]

Has anyone upgraded the engine on a 1970s vintage doodlebug with the angled engine mounting plate to a harbor freight 6.5hp style engine? Also has anyone mounted a disc brake kit to one of these frames and how did you do it?

 

[DaddyJohn]

If I were to do such a thing, I'd cut the angled motor plate out entirely, then make a new one to weld flat onto the lower frame rails.
Should be pretty straight forward and allow for the room you need.

 

[Yukoncornelius]

Would this engine work as a minibike engine? https://www.princessauto.com/en/detail/7-hp-208cc-ohv-gas-engine/A-p8445405e

How would I hook up a throttle?

 

[DaddyJohn]

Would this engine work as a minibike engine? https://www.princessauto.com/en/detail/7-hp-208cc-ohv-gas-engine/A-p8445405e

How would I hook up a throttle?

Yes, it looks like your typical Honda clone (Predator) style engine.
You should just be able to pass the end of the throttle cable through the throttle linkage and cinch it down.