max RPM of push mower engine is dictated by length of the blade. Blade tip speed cannot exceed 19,000 fpm which translates to 3627 for 20 inch blade 3454 for 21 inch blade and 3298 for 22 i.ch blade, but max speed can also be lower when dictated by the mower OEM>What is the engine RPM setting of 12H802-1987-B1