I had cause to pull apart a Briggs & Stratton recoil starter sprag clutch the other day. The ball bearings inside the sprag clutch did not engage every time. So on some pulls, my arm felt like it was coming free of the socket.

After removing the retainer cover I cleaned a brown muck out of the clutch housing and from the six ball bearings. Some of the bearings were rusty and all had their shiny coating dull and damaged. I was about to put it back together as it was, when I realised the ball bearings were very similar in size to some I pulled out of a bicycle a couple of days earlier. Found the bike bearings and got out the vernier to check. Yep, nearly the same size.

So for anyone with a Briggs & Stratton sprag clutch (recoil pull start) that is not engaging correctly... The ball bearings you find behind the crank (pedals) of most bicycles are a suitable replacement.