CAMS AND VALVE ROCKER ARMS

[LOUD MOUSE]

I want to pass on something I've seen over the years and never mentioned to this forum.
HONDA issued a part 14431-268-305 (VALVE ROCKER ARM) which contacts the cam high lobe and opens the valve.
This part has a design change from the early/previous part as to the location of the hole to supply oil to the contact area from near the pivot point to the center/middle of the contact area.
All the new ones I've seen run don't seem to have a smooth/flat contact area.
What I find is that the part wears at that contact area and damages the cam lobes.
I mention this now as I just disassembled a DREAM head which had VERY LITTLE run time and all parts were scored/damaged and are useless and I'll need to replace them.
This isn't the first time I've found this but today I'll offer this to the forum.
If you have/or do run them good on ya but I don't install that design.
Just a FYI. ..................lm

[G-Man]

LM

Many thanks for that. I have found something similar and I didn't know whether it was the way the biked had been used / maintained.

I think the problem is that the hole in the middle of the contact area actually interrupts the lubrication film. If it was pressure-fed it might work but we know these bikes don't have much oil pressure.

I have dismantled some very early heads with the older style and they have survived very well in comparison.

G

[PhilD]

LM makes an interesting observation and GMan may well be right in thinking that the low pressure oil feed is disrupted by the central oil feed hole in the modified rocker arm design. I wonder if the design was modified because wear occurred due to poor maintenance and infrequent oil changes rather than any real design defect. I've just rebuilt my 1964 CB77 engine which has done almost 50,000 miles and has the early rocker design, there was no visible wear on either the rocker arms or the cams
PhilD.

[G-Man]

Phil

That's some mileage! Yes I was quite surprised at the wonderful state of cam and rockers in some otherwise rough heads found at auto jumbles.

Last week I was reading about how the oval holes produced by oblique cross drillings for automotive shell-bearing cranks caused problems with lubrication. Small holes drilled perpendicular to the crank pin worked better with a horizontal gallery.

Hydrodynamic lubrication works well on smooth uninterrupted surfaces.

G

[G-Man]

I was looking for some parts this afternoon and found this CL77 cam and rockers. Interestingly three of the rockers and cam lobes were fine but the forth one and the cam it was running on were toast.



It may be a coincidence, but this is the only lobe with the little oil hole.



I compared these rockers with some very early (1960) Dream rockers and it's interesting how the shape changed.



G