The Throttle linkage
This was a right laugh, the PO (previous owner) said "I don't know why but it won't go up hills in anything higher than 2nd". I confirmed this coming back to Swindon from VanFest when going up Birdlip hill. He made it but only very slowly in 2nd.
The reason for this was purely down to wear
and lack of maintenance, unusual really as other mechanical parts were in
relatively good nick.
The reason for the slowness up hills was due to the fact that the throttle could not open more than 1/4. The slack in the throttle system accounted for the other 3/4. I made all new parts for the linkages and bushes and there is no slack in it now, there is full range of movement from closed to open.
I cannot confirm that the defect has gone away until he is back on the road so you may have to wait a while....
And yes I can confirm that the excessive wear was responsible for the total lack of speed. Ok, he's not exactly fast but he will rev a lot more freely now.