That's an interesting report that probably wouldn't get through in most magazines these days!
I wonder if it was a new bike or from a dealer "used" stock? My own was a 1950 tele-rigid chariot & would eventually reach 60 plus a bit, but was much happier cruising at 55mph & gave 55mpg overall - but that allowed for easing the throttle back once cruising.
I had none of the running problems described. Mine had the (guaranteed to leak) pre-monobloc that I sorted & Tony Cooper rebuilt the magneto for me, retaining the manual A&R. A friend with a plated & screwed ankle could start it easily.
A bit of retard pulling around an uphill roundabout in 3rd, with throttle and advance matched on the exit was typical of the flexibility.
