Briggs were pull start, usually with a removable starter. 125cc class could be pushed by hand, but were usually pushed by ATVs, and the 500cc had to be pushed by ATVs. In a pinch, we'd use already started karts to help out, but the clutches were a booger sometimes, due to placement on or near the steering wheel, and half the time we'd have to start the first kart again.
The last motor I ran would allow me to pull a wheelie from coming out of the turn all the way down the straight, and into the next turn.
I'd have to tap the brake or blip the throttle to get the front down. It would do it more as the track came in with the blue groove.
I bet the porting must have been interesting on that last one.