I swapped out my .40 2-stroke with a 4-stroke OS Max .70 for my GP Cessna 182. I haven't flown with the new engine yet, but I ran a few tanks for break-in and the engine vibrates the plane quite a bit. Is this common to 4-stroke engines while the break-in period? I'm using 11x7 3-bladed prop.

Yes, they do seem to vibrate more at high speeds.
At least my Saito 100 has more vibration at high RPM.
Offgridman