My 47cj2a normally would hit a max speed of 60mph. Last year I dropped the timing a tad as it was running a bit hot. I think I retarded it too much. Also, when I pressed the pedal to the floor, the butterfly didn't open 100%. So, I added a degree and a half to the timing, took my gas pedal bracket off, welded up the worn holes and pin and redrilled them. This allowed a full push of the throttle linkage. Now she is back to the 70mph top speed. Interesting but simple fix.