A WARNING
Gentlemen, two purchaser of the clutch push rod mod have contacted me this last week. Both bought the kits several weeks ago but have only just now got round to fitting them and both have had the same problem. It transpires that not all C23 outer clutch plates and all C26 thrust plugs are the same. If you look at the C23 you will see that the outside of the centre where the thread is has been raised outwards, presumably by swaging, in order to give enough metal to insert the thread. All the replacement C26s so far supplied are exact copies of my own which has about a 2 mm wide undercut where the thread abuts the hexagon head. Clearly one cannot take the thread right up to the hexagon. However, it seems that Vincents did not always deform the metal by the same amount and not all the raised portions have the same height. I have now measured two of my own and find the heights to be 2.7 mm and 1.9 mm. Unfortunately some are lower than this and for these Vincents have reduced the width of the undercut at the end of the thread on the C26. The two people who have had a problem have screwed in the replacement C26 and it has gone in so far that the thread on the C26 has passed right through the thread inside the C23. This note is a warning to anyone else who has purchased one of my kits and has not yet fitted it. Please check very carefully whether C26 has passed almost all the way through C23 before tightening it. If it has please do not tighten it or you risk damaging the thread on the nut.
There are two possible solutions to this problem. One is to fit a 2 mm thick washer under the head of the C26 before it is screwed in. This will solve the problem for anyone who already has one of the kits but has not yet fitted it. The other solution is to change the design of the C26 and to continue the thread as near as possible to the base of the hexagon. A new batch of nuts is on order and fortunately this problem, which has only surfaced this week, occurred early enough that I have been able to ensure that all the new batch will be of the newer design.
To reiterate
1) if you have already fitted the kit and C26 tightened into C23 with no problem then leave well alone. You have no problem.
2) if you have yet to fit the items then please do so carefully and check that the outer part of C23 has been raised outwards by 2 mm or more. If not then either get a washer made locally or contact me and I will get some made.
3) if you are still waiting for a kit to be sent then it will have a modified C26 or a washer can be sent if you need it.
Sorry for any inconvenience.