Peter Johnson always keeps an eye on this blog and is kind enough to share his recollections with me by email. Peter’s comments on the clutch:
“The original clutch was used at first… Sadly, the splined hub was soft, and kept sinking onto the output shaft… Went to see an old man who had an engineering firm close to home – wonderful place full of machinery! Only him left, sadly, to hob a new spline in better material. He suggested the simplest fix was to make a simple washer/spacer out of cast iron, grease both sides and place it between the shaft shoulder and clutch – it was very effective. I think it was hobbed with the right spline. Previously, I needed to adjust the clutch pushrod clearance between races. Now I didn’t need to. Just checked before a meeting.
However, as time passed and I was given/bought more bits, this (clutch currently fitted) came up and, being Norton, plates were readily available. Lighter, more efficient and simpler. Not sure what happened to the original”
Thank you Peter.