Wow! What a flashback.
I had the same bike, but in '72 it was called an F5 Bighorn.
That was the second bike I ever had.
The year prior, I had its F4 Sidewinder 250 brother which was the exact same engine except the F5 had a larger bore and CDI ignition.
That engine was a torque monster, and virtually indestructible.
I had that bike and engine forever, up to the late 90's.
I did anything and everything on that bike.
I finally sold the engine to my cousin back in '96 so he could put it into an ATV. Probably still running to this day.
I honed my mechanical skills on that engine, and could practically take it apart and reassemble it in my sleep.
I stuffed the engine into an F7 175 frame and my buddy raced it in motocross.
That engine never let me down. Even when the primary gear nut loosened and milled a hole through the crankcase, allowing gear oil to be sucked into the carburetor (carb on the side due to it being a rotary valve engine). The CDI made a 55KV spark that vaporized the carbon and never fouled.
I used 3M industrial epoxy to seal the hole and had no more problems.
I loved that bike.