Hi Julian, it was when I took the head apart that I noticed that it had the correct valves, springs, top collars and collets fitted to the exhaust valves but the inlet valves were standard iron head valves, springs, top collars and collets. I bought a new set of alloy head springs, assuming they would work, 67-0968 valves, 67-0960 top collars and 65-1624 collets. On assembly the exhaust valves look fine using the top collars that came with the bike as can be seen in the 1st picture but on fitting the inlet valves the springs are a lot more compressed due to the top collar being held further down the stem by the collets. Did not try on the bike but pretty sure they would be coil bound. If you look at the 2 pictures above where the arrows point you can see the column that the collets sit in is a lot taller on the SF collars so pushing it further down the stem. Picture 2 is not a new collar but an original one that somebody gave me to check that my new ones where correct.