Hi Grumpy, have had a look at governor arm, spring etc.and it is all good. Have since pulled motor apart. I found a lot of gunk around the governor arm that goes through the crank case, could of this been a slight problem as to the governor not opening properly. Photo 1. I also found a small thin washer in the motor I know it comes from same governor arm (found them when I pulled a motor a part for spares). Without this washer could the lugs for this arm been slightly catching on crankcase and slowing governor for opening properly. No scraping or marks found though. I also found a lot of gunk around the shaft that drives the governor arm, the part that goes in and out, could of this also contributed to governor not opening properly. Photo2. [Linked Image]
[Linked Image]