The Dry Clutch when tightened, clamps Collars(17) & (3) [Said Collars Ilustrated in Fig 1.] firmly together on the Gearbox Mainshaft and if either or most likely both Collars wear at the ends then, as in our case, Collar(3) isn’t pushed away from the machined surface of Clutch Drive Gear(5) [where it sits behind Oil Seal(27)] by Collar(17).
The Collar(17) measurement 'A' (see Fig. 2) taken from my Son’s Dry Clutch was 45.06mm as compared to 45.17mm from the one I obtained [!!who would think just over 0.11mm would make a difference!!! I didn’t take Collar(3) out to measure it, however I suspect that had some wear on it too].
This can possibly be better explained using Fig. 3.
Using the Newer Clutch Drive Gear(5) and its Collars(17) & (3), when the Clutch Drive Gear(5) is pressed down onto a flat surface then it pushes Collar(3) back against its machined housing in Clutch Drive Gear(5) which in turn pushed Collar(17) up showing that there to be a 0.20mm Gap [Note: I am not sure what this Gap should be as can’t find anywhere that mentions it].
Therefore, when Tightening up the newer Clutch Drive Gear(5) and Collars(17),(3) up, that 0.20mm must provide enough free play between Collar(3) and the Clutch Drive Gear(5) machined housing enabling it to spin freely.
On my Son’s Dry Clutch when doing the same, there was a slight Gap between the 2 Collars(17)&(3) inside the Clutch Drive Gear(5) [they had obviusly worn down] and therefore when pressing the Clutch Drive Gear(5) down onto a flat surface it didn’t push Collar(17) up at all and obviously there wouldn’t be any end play!
Consequently, when this it was all bolted onto the my Son’s Gearbox Mainshaft, there was no free play, therefore Collar(3) was pushed firmly against its housing inside the Clutch Drive Gear(5) and the result was, it clamped it all together.
I hope I haven’t made too much of a hash in this explanation, only your feedback will tell me if I am totally up the Creek without a Paddle (and not for the first time either).
I have also ordered some new Collars from DMR-JAPAN [you can't get these Collars anymore from Honda] and when they arrive, I will put some more accurate dimensions down which can be used as some sort of Reference only. Obviously, all new parts would be required to make more of accurate measurements.
ADMIN: Edited to put images inline to make post commentary easier to follow. Fig.3 caption edited to correct item number and add OEM part number missing from the original.