WARNING!!
In reply to SunbeamS7's posting - the bigend bolts on 2¾hp engines are 17/64"dia x 25tpi (not ¼" bsf)(another of Mr Douglas's odd threads!). The original set up relies on a good fitting thread to align the cap with the rod - if these have become worn, it pays to open the threads out to 7mm x 1mm pitch and use Allen Screws for the bolts. Allen Screws have a rolled thread, so are much stronger than bolts with a cut thread. Also, some modern CNC produced bolts have threads that end in a continuous groove right around the bolt - leaving a reduced section at the point of maximum loading (I have heard of several modern bolts failing in use!).
Regards,
Eddie.