I'll try to answer this question best i can. Please anyone else share what you know or if this in incorrect or incomplete.
Not counting the final driven shaft, there are five parts that make up the early version of the chain oiler that came with these bikes.
There was enough concern on this issue by Honda, that two Service Bulletins were issued about this particular chain oiler. I'll try to keep this as 'unwordy' as i can, for the sake of clarity.
Service Bulletin #5 discusses drive chain lubrication adjustment and lists the six parts including the final driven shaft, which make up the chain oiler. The parts referred to in SB #5, are the same parts which can be seen on pages 44-47 of the first printings of the CB750 Parts Manuals.
Before discussing the oiler adjuster, on end of driven shaft (opposite counter shaft sprocket) bolted to crankcase is the "final drive shaft oil guide," or, if you will, splash pan. Oil lying in crankcase went into this "guide" pan, then passing through the drive shaft, thru the felt element and out a hole in shaft to sprocket and chain. If your felt element was inside the shaft but there was no final shaft plug, i suppose it's safe to say there was not enough pressure in the crankcase to push out the felt element and/or you were just lucky the felt element did not come out on it's own. Seems, if i recall correctly, the felt element was sort of a tight fit, but not that tight. This felt element is really nothing more than a sort of porous plug.
Anyway, speaking of the actual oil flow adjuster, there originally was a 1.5mm shim (#27, pn 90443-500-000) washer which held the final shaft plug in a set position, thereby pressing against the felt oil element, inside the final driven shaft, intended to allow only a certain amount of oil to leak thru the felt element, then thru the hole in the final driven shaft and onto the outside of the shaft, spinning the oil onto the sprocket and the chain. SB #5 discusses replacing the 1.5mm washer with a 1mm washer to decrease oil flow or add an "substitute" shim washers of different ticknesses to the 1.5mm washer to increase flow. Use of these different thickness washers was intended to more or less compress the felt element in an attempt to control oil flow thru the felt element flowing out the hole in the final driven shaft.
Service Bulletin #22 refers not only to a different thickness washer but also a "modified oil reserve element" to attempt to control oil flow out the hole in the driven shaft. I've not done enough research to know if there were part numbers for the shims that were different sizes from the 1.5mm shim. SB #22 states this different thickness washer and modified element are to be used on engine numbers before 10,915.
Then, there is SB #17 which discusses adjustment of an entirely new chain oiler adjuster, beginning engine number 26,144. I may be mistaken, but i believe this new chain oiler had a different driven shaft, making the new oiiler adjuster not interchangeable with early felt type.
The K1 parts book shows the early and the later (as noted in SB #17) chain oiler adjuster. In the K1 parts book, i don't see any mention of the different thickness washers nor the "modified element" as noted in SB's #5 or #22.
The original chain oilers were a challenge to adjust properly and keep adjusted. They allowed an oil puddle to form when the bike was parked on the sidestand. With time, the felt would allow more or less leakage or none at all; usually not the case. Honda came out with the longer (55mm) chain guard to deflect the oil to the ground instead of up the rider's or passenger's back. SB #22 mentions all frame numbers before 21,880 could have the "modified" guard installed free of charge.
Writing this, i do remember, again, my rolled up sleeping bag, bungeed to the passenger portion of the seat, getting oil on it, during my trip out and back to California, May 1970.
These chain oil adjusters were nothing more than an attempt to control a deliberately designed engine oil leak.
Would be interested to know if Mark's E100 retains it's early adjuster.