My view, engine parts were painted prior to assembly - no evidence of paint on gasket edges, etc on original motors I have seen. Also, may even be easier to paint the aprts prior to assembly when there is no risk of any grease / oil / other contamination of to be painted surfaces. yes, there are more surfaces to be masked this way, but lets not forget that in mass production they would not be concerned about the need to use "easy fit " masks, and to arrange the paint to avoid critical surfcaes where ever possible.
I would agree with Steve that there seems to be more paint on the cylinder head / barrels. may be it just looks different due to the effects of heat / time, or perhaps indeed they did spray more onto the top cylinder head fin to get a good finish there. Just speculation on my part!
Concerning engine internals, I tend to replace all the chains and tensioners because a) they are still available, and b) they are 40 years old now. That said, I have stripped many engines (40+ now) now in which the rubber rollers were still soft / pliable / undamaged (which I would not hesitate to re-use in a "rider"). Some where the rollers were hard as rock with piaeces coming off them, and some which had simply stood for so long that at the point of contact between chain and roller, a permanent imprint of the chain existed. I suspect the condition is actually down to mileage (and therefore cumulative effects of oil and temperature exposure). added to that, it is far easier to clean up and restore an engine properly if it is totally dismantled (all fasteners readily re-zinced at the same time, no paint on them, etc, etc. each to there own though.
O rings especially, and seals wherever available of course need replacement though.
Valve stem seals though do seem to suffer the most, and always replace / never re-use. Little surprise, they are in the hottest bit after all!
Springs, not at all concerned about -just measure them and re-use if in spec (my day job is in part that of a spring designer the last 25 years or so, and the Japanese knew what they were doing here, even back in '69).
The last set of valve springs I checked (out of my 400-4) were still within factory spec at 108,000 miles, and were re-fitted.
For interest, clutch plates in #5298 were measured up at 103,000 miles and were still within the new tolerance range (and so they went back in too).
Oh, and the original 45T rear wheel sprocket is still the original one at 112,000 miles -use DID / RK heavy duty chains, lube and adjust frequently, and replace at every rear tyre change.
Sorry guys, straying off the thread here!
