Having looked at the options I took the decision to swap the entire head instead of swapping camshafts.
This should be the easier option but is still alot of work so, at 1.30PM Bryce and I started work.
First was to remove the head from the spare engine which we took our time over as we are novices to the Sprint engine. Having learned some valuable lessons though we then moved on to the engine in BRP.
We noticed that one of the lobes on the cam in the BRP cylinder head had been worn flat but worse was that one of the rocker shaft reteining bolts was loos - in fact, it seemed to have no thread on it! These two elements could certainly explain the noisy top end and justified removing this head on their own.
Having got it off though we then found corrosion in the waterways too as can be seen here.
The head from the spare engine, however, showed lots of little signs of being worked on and it has the new cam as well.
Next is a reversal of removal in that time honoured fashion and after 4 hours work we had the new head on, torqued up and the front sprocket back in place.
End of play.
Apart from I just couldn't let it go so at 7.30 I went back out and completed the reassembly of the inlet manifold and exhaust manifold etc. That exhaust manifold was a complete swine though, no matter how many times I tried I could only get 4 out of 5 bolts in - they might be a different combination each time but still only 4 out of 5. I will need to return to this.
So, all back together, 9.30 PM and I try to fire it up. No joy.
The engine will turn but no sign of anything happening. This could be for a number of reasons although I think it's probably to do with the fact that we put it all back together as close as possible to how it was to start with - that is, we didn't time the cam in.
After 7 hours work it's time for a break though so the best option is a week's thought and reflection, the battery on charge and then back to it next week.
Bryce, If you are reading this, are you available next Saturday afternoon?