CB550K - engine rebuild (partial or full)

[Erny]

Thanks Bryan!

[K2-K6]

As Bryan says,  all ok.

To take it underneath that which is needed for good mechanical condition, it can tell us more about the conditions during running so far.

The outer two bearing surfaces show just a flattening of the original boring marks and exactly as you expect to find as witness marks.

The marks are consistent with the design in that the bore size has to have a tolerance in relation to the camshaft journal that avoids seizure and allows for oil film effectively not under pressure.  You can see from the wear marks how far up the "wall" of the bearings that the two depart and no longer touch each other. 
The centre two bearings show their witness marks travelling further than the outer two,  a little like judging plastiguage. Meaning the camshaft has worn into the bearing further on these two,  but a very very small amount.
This would happen if the oil film was unable to support the load as it should. Mostly this is associated with oil condition and specifically dilution/service interval in the engine's life so far.

It seems consistent with the amount of wear in the primary chain too. Those bearings (within the chain) are possibly the highest loaded individual parts in the engine with their lifing giving a good indicator initially of running conditions to that point.

As first stated, it's perfectly normal to see the bearings in the head like this and it's not a fault as such in the overall condition,  just that you can have more of a picture of progress so far in the engine's life.

[Erny]

Small update on my side.

Took carbs and pipes off and did again leak test under these conditions: measured cylinder was in TDC, input pressure ~22psi as per leak tester manual.
result - all cyls:
- shows approx up to 10%-12% leak
- all IN and EX valves are tight (no air or sound goes off intake or exhaust port), air is leaking and is audible around cam chain and oil dipstick, so leaks past the rings (?).

With great weather over last days, I started to consider changing strategy - just fix valve cover, cam and rocker issue and keep riding bike this seson as is. Rebuild (partial or full) can be done next winter.

Before putting bike back to road, I'd like to test oil pressure - where people connect manometer to measure oil pressure? What fitting / tool I shall look for?

[Bryanj]

Thats not a high percentage so should be ok when running as combustion pressure gets behind ring and increases tightness to bore.
For oil pressure either remove the pressure switch and screw an adaptor in there or you have to drill and tap the hexagon "bung" below the points cover

[deltarider]

... or you have to drill and tap the hexagon "bung" below the points cover

Why drill? Can't you just undo it with a wrench?

[K2-K6]

"With great weather over last days, I started to consider changing strategy - just fix valve cover, cam and rocker issue and keep riding bike this seson as is. Rebuild (partial or full) can be done next winter."

I can't see any problem with that.  With the rocker fixed it should be fine and you'll just be planning an "advanced" service to change primary chain etc when it's convenient for you.

Oil pressure, can you temporarily install one of the car type gauge into the pressure switch port?  Then you can measure it when it's fully warmed and running throughout rev range.

[Erny]

I'll look for some gauge.
What level of pressure is minimum needed or which level is "good" enough?

[K2-K6]

A loose description,  but think the oil light switch extinguishes at about 15psi, maximum about 60psi at full speed (will open pressure relief valve cold when revved so you'd not see more than 60) likely to run in range of 30 to 60 psi when hot.

[Erny]

Thanks

One more question - can I consider replacing vavlve seals w/o removing head? I guess it is doable but maybe difficult and special tool to support valves from bottom needed?

[Charlie J]

I used a Sealey VS1542 Valve Collet Remover/Installer to remove the valve springs so I could replace the oil seals without removing the cylinder head. I was a bit apprehensive about using it as I had read some reviews that said the tool was fine for removing the collets but not so good at reinstalling them. However, the tool worked a treat for me. The only slightly tricky part was dealing with the exhaust valves on cylinders 2&3 because of the proximity of the posts for the fuel tank mounting rubbers. But a sharp tap, square on with a 2lb hammer did the trick. I also used the string down the plug hole and rubber band tricks which I read about on this forum.

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[Bryanj]

You have to drill and tap the centre of the plug as its a largish diameter thread, you could also make an adaptor instead

[K2-K6]

Thanks

One more question - can I consider replacing vavlve seals w/o removing head? I guess it is doable but maybe difficult and special tool to support valves from bottom needed?

Good first hand experience from Charlie there. I've not changed any with head installed so just an irrational, perhaps, fear for me, but would leave them if you have no signs immediately of needing to change them.

If you've confirmed the valves aren't leaking and happy with that,  then caution in doing something that may just bend one even slightly (touching a piston crown with one edge) may be a more secure route.  And eventually you'll get them easily if you do further work.

[Erny]

yes, surely it will be better to do it when head is off. Only motivation to replace them now is oil consumption - if after replacing seals oil consumtion will be reduced and only remaining weak place will be rings/pistons.
I assume seals will be hard after 46 years so not sealing properly I guess

But I'm only investigating now what are options/way to do. If too risky/complicated or costly, I'll let it be

[K2-K6]

Certainly I think Charlie's first hand experience out weighs my view, so doesn't appear a big risk.

But through observation of an engine showing oil use I generally seperate as, smoking under acceleration consistently then its normally rings,  with longer run (downhill) with throttle closed,  then emitting smoke just when you open the throttle (single cloud) is ordinarily inlet valve guides as it sucks oil down the valve stems (high vacuum in inlet tract) to be burnt just as you open the carbs again.

Good idea to make a list of concerns that you can then work through later.

[Charlie J]

I changed the valve oil seals without removing the head as I was hoping for a quick fix for my smoking engine. Unfortunately, it didn't fix the problem and I ended up having a rebore, new pistons and rings and a whole list of other items whilst I was at it, resulting in an almost total rebuild!

Charlie