CB550K - engine rebuild (partial or full)

[Bryanj]

Big thing is that the majour part of the work is the time and gaskets/seals to remove and strip the engine, in this case the engine is already totaly stripped so the cost of the chain on top(if you use the Kawasaki one) is minimal.

[K2-K6]

A more philosophical question for Erny;-

If you don't verify the cush drive in rear wheel is ok (thinking in regards to gear change quality) and then try the bike to assess the affect it may have,  then if you take the engine apart and the gearbox all appears ok,  what would you do?
Put it back together without finding "the" fault, or change components at random.

Also for idle quality and smoothness,  I'd set the carbs with the "compression weak" cylinder at less vacuum than the other three to listen and assess if it gives a noticeable change.

I just feel that would give a clearer picture and more knowledge to work from if you determine to strip it later.

[Erny]

After longer time (I had to find energy to start it  ) update

Issue No1 (camsshaft/rocker arm) (see my first post for details)
Today I removed valve/cam cover to check IN#1 rocker
What I found surprised me (!?)
- IN rocker arm #1 has uneven wear (arm was touching cam only partially), at least half part of contact surface is not showing any wear at all. Seems issue is present since new bike 
- Cam IN#1 lobe shows strong wear (pitting incl) where arm was riding. Rest of contact surface does not show any wear
- Deeper inspection revealed issue comes from worn outside rocker arm shaft hole! Hard to believe but yes...
- Comparing how "deep" are shafts for IN#1 and othher shafts (EX#1, IN#4, EX#4) "buried" in valve cover, I found IN#1 is approx 2mm "deeper". Route cause comes from IN#2 shaft too "deep" and consequently IN#1 shaft too deep too that finally meant too narrow seat.

Shafts are all OK otherwise (forgot to take pics), incl IN#1. There does not look to be any issue with engine lubrication, all other cam lobes, cam bearings, rocker arms shows minimal wear I think (see pics).

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My conclusion is that issue is present practically from new bike, camshart to be repaired/replaced, rocker arm to be replaced, valve cover to be replaced, ideally with new improved type

Issue No2 (identified in previous posts here are probably worn primary chain)
I removed oil pan, see video of primary chain. Looks worn too much or not?
https://youtu.be/a1k28x_15lQ


Now, question to experts here:
- I assume cam lobe shall be repairable (hardwelding, grinding), but when I have it open, I'm thinking about alternative cam (something like Web Cam 358a or cam from CB650?) - what's your view on these cams and their effect on riding? Repair of my cam won't be for free anyway (if I find somebody to do the job).
- how to inspect cam chain and tensioner properly, having removed valve cover? Or, do I need to remove head/cyls too?

This will drive my next steps - if I'll continue stripping or "just" fix cam/rocker issue.

[Erny]

remaining pics
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[Bryanj]

The modified cover didnt come in til 77 and i see no reason the original cover could not have a thinwall bush fitted, wear happens when the shaft rotates a "quick" fix is to put an O ring in the holefot the pin on theouter cap to trap and stop the shaft rotating

[Erny]

Not sure I understand fix with O-rings - can you pls explain it more?

[K2-K6]

"- how to inspect cam chain and tensioner properly, having removed valve cover?"

Initial rough check of camchain;- just try to lift the chain at the highest point on the cam sprocket as it compares the chain pitch with the tooth pitch. Any more than approximately 1mm and it's worn to excess. Meaning that a new one cannot ordinarily be lifted, 1mm and you'd consider planned replacement,  3 to 4mm definitely finished.

Tensioner, again a rough first impression of if it's adjusted, turn the crankshaft backward 1/2 turn and check for slack on the front chain run if you can access it. An old bicycle spoke may allow you to just hook the chain to pull it back toward the rear of engine to assess if there's too much play.  Or make a little wire hook to do this.

It really gives just a first impression of anything wrong. The cam chain lasts quite well though but obviously you'd change it if you did the primary one.

[Erny]

Thanks all for advices and explanation

What about primary chain? Based on video and your experience, is it possible to say of chain is on its end of life?

[K2-K6]

Adding to the above, the chain disguises it's wear really well and is unlikely to fail. They just go on getting more and more loose but with the tooth form and design (the way the chain changes as it bends)  keeping it running quite effectively.

The limits for this engine are particularly, that it will end up touching the crankcase casting, and that it will make more noise when idling.

This one is not so urgent that you'd have to stop using it and change immediately,  but certainly to plan for work to get the parts and complete when convenient for you.

As Oddjob says, the cush drives need to be considered if you are stripping to change the chain.

[Erny]

OK, thanks for your feedback. This is my feeling too - so highly likely I'll open engine to replace primary chain + cush drives

[deltarider]

It is with hesitation that I show you the pics of a new and a used primary chain. I found them on the German site. As told before, the chain on mine has now served over 138.000 kms. I am still far from the guy who's CB500 at 220.000 kms still had the original chain. These chains stretch no doubt, especially in the beginning; more than once have I read that somebody became dissappointed when in less than 15.000 kms after replacement the new chain was as audible as the old one had been. As far as eating the crankcase, we'll see; I volunteered to be the guinea pig. Note that the chains shown here, are called new and used. I avoid the word 'worn', because I don't know if that is the case.
(Courtesy Spargeljo)

 

[Charlie J]

Just to confirm what Oddjob has said, here’s a photo showing where the primary chain had chewed into the crankcase of my CB500 K1

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[deltarider]

This is what a German engineer 'Maschinenbau' explained me. Chaindrive always implies play at the loadless part. Just watch the secundary drive chain. A tensioner is only needed when a chain travels over 60^o to the horizontal. On our bikes the crank turns CCW seen from the LH side, so the lower part of the chain is loadless and will show play. That play there doesn't worry me.
Here is how I see it. Before I entered the internet, I had never heard of the primary chain causing problems, not from Honda mecs nor was it described in Dutch and German magazines.
Don't get me wrong. I am not denying the chain can eat in the crankcase. After all I myself once discovered an aluminium chip in the oil. When? Some 70.000 kms back... And there are also lots of photo's to prove it. You can make life easier for that chain by having the ignition timing even for 1+4 and 2+3 and the carbs balanced so that all 4 cylinders work as equal as possible.
So, would I replace that chain when the engine is opened? Definitely!
Would I open the engine just for that? No.
 

[Bryanj]

Yes you only get play in the unloaded side of the chain but when that gets excessive, which is a shorter time when an idiot owns the bike(harsh use and little service) the movement allows the chain to act like a milling tool on the alloy and yes i have seen one eat all the way through into the oilway, i have also seen one, and only one, worn out crankshaft but personaly have never actualy seen the worn out cam covers the yanks go on about.
Different countries have riders with different riding styles as Yamaha found out with the RD350LC when after extensive testing they sold it to UK riders who promptly kept blowing exhaust gasket causing, i think, 4 different modification "kits"

[Charlie J]

  That made me smile Bryan “when an idiot owns the bike” Just wanted to point out that although I own the bike in the photo I posted, the damage was caused some 30 years or so before I rescued it from where it had been abandoned in a shed. Although, that doesn’t necessarily mean that I am not an idiot