When I said roughly I meant roughly.
Honda domestic mowers mostly spin at 3200 rpm because it makes them a quieter
The same engine with the same carb in a commercial mower spins at 3600 rpm.
Victa put out the "silent Vortex engine" which was exactly the same as every other powertorque except it was governed to 3200 rpm as well.
Biggs engines are all good for 4500 after which they choke which is good cause at 5000 they self destruct.
Various machine makers specify different governed speeds and most give you the speed +/- 200 rpm.
Now you asked for the MAX rpm and the MAX safe RPM recommended by just about every engine maker is 3600 rpm.
As for walk behind mowers, the powers to be in the government decide on what is the maximum safe blade tip speed for various classes of mowers.
Like all things Nanny Sam keeps on dropping this every time some 1/2 wit manages to cause damage to himself or some one else.
Thus some walk behinds get the speeds lowered to comply with the regulations.
Down here all walk behinds leave my shop spinning at 3500.
A lot of the customers come back saying it has never cut so well from new.
A few hundred rpm makes a massive difference to the quality of cut particularly over there where swing back blades were banned to prevent Aust mowers being imported so you lot are stuck with bar blades on 16" to 24" walk behinds where they just don't work particularly well at all, but that is corrupt politics, nothing you or I can do about that.