Author Topic: cam and rocker wear (Read 2085 times)

rtnoble · « **on:** March 14, 2011, 05:32:52 PM »

Howdy from B'ham!

Old member #3229, but I had to re-register??

Any how,
Torn down top end on '80 650 and rockers (2) are pretty scorred. I bought a new box on ebay and it looks good. Will pull sustitute rocker arms. QUESTION: is mixing used rockers on an old cam OK, or am I asking for probs? I don't see any way around it. Honda wanys $70 per rocker. Will post pics when I figure out how! How do you do that?? Rock on cammers!

Russell
1980 650 bought new in 1980.

rtnoble · « **Reply #1 on:** March 14, 2011, 05:41:18 PM »

checking...

TwoTired · « **Reply #2 on:** March 14, 2011, 05:41:45 PM »

The wear surface to really worry about is the followers against the cam lobes. Try and keep those associated. Otherwise, use beak in lube to get them reseated/married again.

rtnoble · « **Reply #3 on:** March 14, 2011, 05:44:23 PM »

see far right rocker pad... need to repace...will it wear in and mate up or is this a problem down stream? thanks!

TwoTired · « **Reply #4 on:** March 14, 2011, 05:48:21 PM »

The follower faces are surface hardened. Does it look worn through? What does the corresponding cam lobe look like?
Can you polish the follower faces?

rtnoble · « **Reply #5 on:** March 14, 2011, 05:51:30 PM »

2tired,
It is pretty scored. See pic. It catches my fingernail. Cam lobe looks much better that the pad. I can do a zoom? Would that help?

Thanks,

Russell in B'ham

TwoTired · « **Reply #6 on:** March 14, 2011, 06:00:41 PM »

Just to be clear, you are putting a less than smooth follower against a brand new cam lobe? Is that right?

If so, either replace that rocker, or polish it as smooth as the cam lobe faces. If during polishing, it suddenly get a lot easier to make smooth, then you've polished off the surface hardening and it will have to be re-hardened or replaced.

If you still have the original rockers and they are still matched to their respective lobes, can you not use those?

rtnoble · « **Reply #7 on:** March 14, 2011, 06:14:30 PM »

No new cam.

Torn down for oil seal at head lip leak (notorious). Found bummer rockers. Was gonna go back as-is with old cam and box of rockers, but decided rocker faces looked too bad...hence replacement with used ones.

see pics.

2-tired, I have been riding this bike for 30 years, and I am good with a wrench...just dont want to do anything stupid. Seems like i recall from the old days with cars...replace lifters with cam...does that hold here?

will post close ups shortly

thanks,

russell in bham

rtnoble · « **Reply #8 on:** March 14, 2011, 06:23:13 PM »

see wear...

rtnoble · « **Reply #9 on:** March 14, 2011, 08:04:39 PM »

OK. I will replace and button up. Thanks all..

Russell in Bham

TwoTired · « **Reply #10 on:** March 14, 2011, 09:58:35 PM »

That's not a good wear pattern. The contact area is supposed to spread across the entire flat area. On of the two surfaces is convex and should be replaced or reformed/reground.

Yes, the lifters/cam followers and cam are considered matched and should be replaced together usually. Exception is if you can measure conformity and restore a contact area to spread the load across the flats evenly.

How many miles on that wear pattern?

faux fiddy · « **Reply #11 on:** March 14, 2011, 10:14:21 PM »

Now you have me concerned about the rocker I replaced with a used one. Will it (the new one and/ or the camshaft lobe) need to be machined to conform to each other? As it is I just swapped them out and buttoned it up.

The ODO on the worn one is at 10,000.

TwoTired · « **Reply #12 on:** March 14, 2011, 10:27:20 PM »

Hey Tree,

Is that a 550? That is the wear pattern that occurs with the dreaded rocker shaft wear on the early Pre-77 CB550s.
If it is still shiny, it will work ok. But, the more focused the contact area, the more likely wear and galling can begin. Once galling starts, it's just a matter of time before the cam profile gets altered.

http://forums.sohc4.net/index.php?topic=20408.msg212239#msg212239

Cheers,

faux fiddy · « **Reply #13 on:** March 14, 2011, 10:38:06 PM »

It's a 74 350f. The cam looked good, no scoring but I didn't use a micrometer to check the surface. Definitely some of the hardened surface comming off, and on only one rocker.

TwoTired · « **Reply #14 on:** March 14, 2011, 10:59:42 PM »

I haven't worked on the the 350F.
The Chilton book shows a rocker shaft that extends under two rockers. So, it really shouldn't have the problems the early CB550s sometimes do.

The good news is that it is still shiny, not galled. But, I can't explain why the contact area isn't fully involved across the entire flat as it should be.

Maybe BryanJ can shed some insight on your specimen? PM?

Sorry.

bryanj · « **Reply #15 on:** March 14, 2011, 11:23:57 PM »

350 can't help never seen one (they were not imported to UK)

650 use a used rocker but gently stone out the mark on the cam ---which is not hardened anyway A stone, before you ask, is like a solid piece of carborundum

faux fiddy · « **Reply #16 on:** March 15, 2011, 06:41:17 PM »

Quote from: TwoTired on March 14, 2011, 10:59:42 PM

The good news is that it is still shiny, not galled. But, I can't explain why the contact area isn't fully involved across the entire flat as it should be.

Sorry.

The hardened surface is definitely missing in that corner. I did smooth it off with a stone, and while it helped you could still feel an edge where there was a distinct ledge of a maybe couple thousandths.

I opted to use a part out of a different motor that looked better and felt smooth with all the hardened surface intact.

Is there something that is extremely bad to use a rocker that was worn in on a different motor ? Seems like as long if it is adjusted right it would be just the same.

TwoTired · « **Reply #17 on:** March 15, 2011, 06:56:43 PM »

A good part is better than a bad part. Wearing surfaces learn to fit together at a microscopic level. Polished parts wear less and that is essentially what happens during break in, the parts polish each other until they fit together comfortably/smoothly.
Introducing a different half to the mated surface, begins a new round of polishing and wear in cycle.

If you have some dychem blue you can coat the mating surfaces, and do a dry fit, rotate the cam and then see where the contact areas are with the new association. Then decide if something else needs to be ground or replaced to correct any ill geometry.

Or, you could just run it to see if it wear out faster than you'd like. Kinda depends on just how much over-designed Honda made the engine.

I only know that when we went to high lift cams with way stronger valve springs, cam lobes needed full broad contact with the followers to keep from galling and rounding the lobes off. But, if it lasted through break in, it was usually good for a long long time.

I don't know if I helped or boosted your fears, though. Sorry. Just sharing some experiences.

Cheers,

faux fiddy · « **Reply #18 on:** March 15, 2011, 08:49:08 PM »

Quote from: TwoTired on March 15, 2011, 06:56:43 PM

If you have some dychem blue you can coat the mating surfaces, and do a dry fit, rotate the cam and then see where the contact areas are with the new association. Then decide if something else needs to be ground or replaced to correct any ill geometry.

Or, you could just run it to see if it wear out faster than you'd like. Kinda depends on just how much over-designed Honda made the engine.

I only know that when we went to high lift cams with way stronger valve springs, cam lobes needed full broad contact with the followers to keep from galling and rounding the lobes off. But, if it lasted through break in, it was usually good for a long long time.

I don't know if I helped or boosted your fears, though. Sorry. Just sharing some experiences.

Cheers,

Well once when the blue dye was being used and the cap appeared to be on, I bumped it over to find it wasn't twisted on tight. That's more what I'm afraid of. Good Part ,Run it!

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Author Topic: cam and rocker wear (Read 2085 times)