Theres two prevailing trains of thought around here, one camp believes the engineers that designed the engine know what they're talking about and followed the 50hr breakin recommendation to a "T", then theres the other camp that believes in past experience that calls for breaking it in like how your gonna run it.
So all you got to do is pick your poison
I decided to stay as close to the manufacturers recommendations as I could and kept away from full throttle and didn't lug the engine for the 1st 50 hrs.
My BX23 doesn't have a tach so I went by throttle position. With 3 oclock being full throttle and the rated pto speed being a hair under that, I kept mine around 2:30/2:45 oclock and would drop the rpms every 20 minutes or so for a moment or two to give the cylinders a good oil splashdown, then I'd run it back up again.
At around 35 hrs I noticed that the engine hardly puffed white/blue smoke when I engaged the pto and also that the engine didn't dip it's rpm as much as when new. To me this was a good indication that the rings had seated but I still stayed away from full throttle until the magical 50 hrs.
Anyway, I think it's easier on the pto and implement drivetrain to engage it at less than full throttle (or breakin throttle) so I usually engage at about the 1:30 oclock position then run it up. The key being to find the rpm where the engine doesn't lug as much and also where the pto/implement drivetrain doesn't "jam" into motion as abruptly, the happy medium so to speak.
You may have to be alittle higher on the rpm due to the additional load of the bagger but you should have the pto lever in "both" position.
You'll need to experiment to find a good working rpm and engagment rpm but other than that you should get highly impressed on how well your BX finish mows and how well you feel doing it
Good luck
