How stealthy can a gas engine putting around be?

But yeah if I was in the market for a brompton I'd go for a clean one without an engine mod. First thing I'd think about was what kind of stress was put on that front axle and tiny fork and how much longer would it be till it snaps on me one day. I'm just weary cause non motorized folding bikes are usually not made to handle such stresses on certain parts of the bike. I'd opt for a full size mountain bike if I was adding a gas motor to one at least the frame and fork would better handle the torque and stress.

If you part them out you might sell them soo much easier, someone will want the bike only and for the motor you'll find a select group of people that will want to motorize everything but don't want the bike.