Author Topic: CB550K - engine rebuild (partial or full)  (Read 7519 times)

Offline Charlie J

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Re: CB550K - engine rebuild (partial or full)
« Reply #60 on: February 20, 2021, 03:06:23 PM »
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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Offline deltarider

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Re: CB550K - engine rebuild (partial or full)
« Reply #61 on: February 20, 2021, 04:43:28 PM »
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 60o 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.
 


Offline Bryanj

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Re: CB550K - engine rebuild (partial or full)
« Reply #62 on: February 20, 2021, 05:01:17 PM »
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"

Offline Charlie J

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Re: CB550K - engine rebuild (partial or full)
« Reply #63 on: February 20, 2021, 05:11:48 PM »
  :) :) 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 :-\

Offline Bryanj

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Re: CB550K - engine rebuild (partial or full)
« Reply #64 on: February 20, 2021, 05:24:53 PM »
 : :D Perhaps i should have used the word initialy berween idiot and owns!!!!

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #65 on: February 21, 2021, 04:51:39 PM »

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.


Checked using proposed method (I did not released tensioner) - practically cannot lift it or just very little, but can move left/right easily (holding it at the highest point).
So, I would say chain is OK?
CB750K7 US model (1977)
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Offline K2-K6

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Re: CB550K - engine rebuild (partial or full)
« Reply #66 on: February 21, 2021, 05:31:58 PM »
That sounds fine with no real wear at all.

It doesn't matter if it's tensioned or not as you are effectively comparing the chain pitch with the sprocket pitch, with no realistic slack it shows it's virtually as new. 

A chain can be tensioned as much as possible,  but if worn you'll still be able to pull the links away from the sprocket at the centre of it's engagement.  If you can't it's definitely good.

They move/slide slightly side to side,  all seems fine.

Offline deltarider

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Re: CB550K - engine rebuild (partial or full)
« Reply #67 on: February 22, 2021, 12:19:58 PM »
Erny, your finding doesn't surprise me. On the German site camchains are often found not worn.

Online McCabe-Thiele (Ted)

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Re: CB550K - engine rebuild (partial or full)
« Reply #68 on: February 22, 2021, 01:58:40 PM »
I found this section on chains very interesting.
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Trigger

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Re: CB550K - engine rebuild (partial or full)
« Reply #69 on: February 22, 2021, 07:05:27 PM »
Erny, your finding doesn't surprise me. On the German site camchains are often found not worn.

The Germans must ride about like Old men.
Out of the hundreds of SOHC/4 engines i have fully rebuilt i have only found a couple of cam chains that had minimum ware. It is still a false economy in my book as, a STD DID cam chain is only about £20 and will last at least 30,000 miles. That is about 66p per thousand miles and when most owners of classic bikes only do about a thousand miles a year, that is a lot of years from a chain  ;)
« Last Edit: February 22, 2021, 07:11:13 PM by Trigger »

Offline robvangulik

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Re: CB550K - engine rebuild (partial or full)
« Reply #70 on: February 22, 2021, 07:46:26 PM »
Erny, your finding doesn't surprise me. On the German site camchains are often found not worn.

The Germans must ride about like Old men.

You are aware that Germany is the only land in Europe, if not the world, where still are roads where it is legally possible to ride full throttle?
And I know from experience that most German bikers aren't afraid to do so.... :)

Offline K2-K6

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Re: CB550K - engine rebuild (partial or full)
« Reply #71 on: February 22, 2021, 09:22:44 PM »
I understood the thread focus was to assess if the motor needs to be split at this time to replace chains etc. Rather than avoid cost,  but more for Erny to get realistic appraisal of if and when it would be sensible to carry that out.

Obviously, the problem with the rocker shaft and it's effect on running brings that to urgent scheduling, but cam chain is ok and primary serms medium worn and so not absolutely required immediately if may be better to complete next winter.

As already noted through the thread,  camchain replacement is entirely sensible whether bad or not, if the crankshaft is coming out.

Clearly the two chains wear at very different rates,  but then they are completely different engineering solutions compared to each other.

Offline deltarider

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Re: CB550K - engine rebuild (partial or full)
« Reply #72 on: February 22, 2021, 09:47:29 PM »
TBH DR I don't think a lot of chains are worn, it's more to do with economy, whilst the engine is down it's false economy NOT to change the chain.
I agree. I just said that Erny's finding didn't surprise me, having seen the findings on the German site. I didn't suggest not to replace it, once the engine is open. I'd do it and every mec in the trade does, even when the chain is not worn. What I'm afraid of is that readers will open up engines for the wrong reason. Actually the best video's I've seen about rebuilding CB's are by Germans. Very thorough (gründlich), very detailed.
Riding like old men? The Germans? You must be joking. It's the only country on the planet, where they have no national speed limit*. At 140 km/h one can hardly keep up with... local traffic.
*Which is a shame actually. Friends in Germany have informed me that this is because of a strong lobby by carmakers like M-B and BMW.

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #73 on: February 22, 2021, 11:54:20 PM »
Just coming from garage, cam is out, next findings for your kind feedback, please - cam bearings in head.
Collateral info - bearings in valve cover are perfect, cam does not show wear on bearings.
From my point of view they do not look very good, hoping you will say it is normal wear (17k miles?)
All 4 bearings on pictures here

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CB750K7 US model (1977)
CB550K1 US model (1975)

Offline Bryanj

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Re: CB550K - engine rebuild (partial or full)
« Reply #74 on: February 23, 2021, 03:21:34 AM »
Aint just normal, they look in very good order

 

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