Well so much for the Roller tip...gonna give it a rest, thanks for the info.....But the F3 # chart has me a little confused ? my Eng id # is 310000, according to this info somebody did a misprint and several other sites also, they state after the eng id # E or F could be common ? http://www.hondachopper.com/engine/engine_mods/modifications.html
What I printed above is what the Honda shop manual states. However, the Honda Motorcycle Identification Guide lists the 78 CB750 as:
Frame CB750F - 2200001 ~
Engine: CB750FE - 3100001 ~
The Honda Parts Fiche agrees with the Honda I.D. guide (rather than the shop manual), and shows the same head used for both 77 and 78 models.
There is a Honda code change for the head. It is my understanding that later heads had hardened valve guides installed as a means to retard rapid guide wear. There were many heads that had the guides changed under warranty. I have a friend that did many of them while he was still a Honda Mechanic "back in the day".
My 78 is currently at the Corbin factory, so I can't look at that bike's numbers right now.
The head chamber for the F2/F3 was domed to accept larger valves. The piston had to be domed to retain Compression ratio. The doming of the chamber increased the valve stem angle, and the side loads that the rocker placed on the valve stem throughout it's movement arc.
It is not just the guides that wear. The adjuster tip puts a divot in the valve stem tip, as well as mushrooming the adjuster tip. Grinding the valve stem tip flat, changes the valve geometry (for the worse). Mrieck found "lash caps" to restore the valve overall length and maintain the proper geometry. Almost certainly, the valve face and seat need regrinding if the guides have worn bad enough to yield an oil smoke out the exhaust issue.
A roller/adjuster at the valve would certainly help the longevity of the valve guides/valves, if only it were available.
I once toyed with the idea of putting concentric cams at the rocker pivot for adjusting clearance. Then adding the rollers to the rockers at the stem interface. Works in concept, but the cost will probably not make it very "popular".
Cheers,