Author Topic: CB550K - engine rebuild (partial or full)  (Read 2069 times)

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #15 on: October 21, 2020, 11:38:05 PM »
What I think is not good is that rattling noise (video does not capture it perfectly....). That I think cannot be from pistons/rings?
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Offline Bryanj

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Re: CB550K - engine rebuild (partial or full)
« Reply #16 on: October 22, 2020, 01:28:28 AM »
Unfortunately i cant play videos on my dumfone but i will say that 90% of rattles are uneven running.
OK take the sump off and see how much play is on the primary chain, you can also get a finger in to see if it has been rubbing the oil gallery. 550 is not normally as bad as500 but can still hit if worn.

Offline Trigger

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Re: CB550K - engine rebuild (partial or full)
« Reply #17 on: October 22, 2020, 08:08:24 AM »
I always find it hard to comment on things like this as, you will not know until you take the engine apart. What ever it is it doesn't sound good.
Compression seems good but, a test is no guarantee on on a engine this old, just look at Julies thread and the state of her pistons and that had good compression, started on the button first time everytime  :o

Offline deltarider

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Re: CB550K - engine rebuild (partial or full)
« Reply #18 on: October 22, 2020, 09:07:04 AM »
Let me begin with stating that I am an amateur and I give my opinion for a better one. Having said that, I don't hear much that would worry me. Personally I like my idle a bit higher though. I myself have never managed to do a compression test right (I know: chokes open, throttle wide open).

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #19 on: October 22, 2020, 10:29:14 AM »
OK, hot comp test I can do.
Shall I also do it as dry and wet (spoon of oil into each cyl) ?
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Offline Bryanj

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Re: CB550K - engine rebuild (partial or full)
« Reply #20 on: October 22, 2020, 05:28:40 PM »
Wont hurt, i think the book calls for 140 hot

Offline K2-K6

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Re: CB550K - engine rebuild (partial or full)
« Reply #21 on: October 23, 2020, 11:37:54 PM »
The video sounds quite noisy to me,  but more chain type than other.

As mentioned already,  difficult to fully appreciate remotely but the audio if anything seems fairly clear playing it here.

If you video it the same agian but stand it on the ground and in first gear,  then let the clutch out until it only just starts to bite. This may give an indication (if it goes quieter) of primary drive noise as it will tension it rather than oscillate.

It'll be interesting to hear if you get any change to the noise.

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #22 on: October 23, 2020, 11:42:32 PM »
OK, I can test this weekend and post here, so warm up, engage 1st gear, pull clutch that is starts to move bike, right? Will be difficult to have 3rd hand but will try  ;)
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Offline K2-K6

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Re: CB550K - engine rebuild (partial or full)
« Reply #23 on: October 23, 2020, 11:47:40 PM »
OK, I can test this weekend and post here, so warm up, engage 1st gear, pull clutch that is starts to move bike, right? Will be difficult to have 3rd hand but will try  ;)

Fix camera pointing at bike, first gear not to drive along but only just get the clutch to start dragging but brakes on.  Should pre-load transmission and tension primary drive just enough to take out "flip flapping" would show if the chain is worn if noise gets less.

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #24 on: October 25, 2020, 10:42:07 PM »
Small progress today

Engine warm-up made (approx 8km):

1. Idling + test of noise change after gear#1 enagage:
you can clearly hear that idle is not 100% regular, there are moment engine rises revs, even I felt during ride on low RPMs like engine running on 3cyl only occassionally... This is new behaviour to me. It feels like I ususally feel after bike washing (I did 1 week ago), engine does not rev more than 6k (feels like ign issue)

- time 0:08-0:15 - clutch fully pushed
- time 0:28-0:36 - clutch fully pushed
=> Rattling seem dissapeared

- time 0:58 - backfire (pipe#2?) - this happens to me for the first time, probaly linked to cyl#2 too rich (as was unable to fix that since long time|

Video here: https://youtu.be/gwZVUlbaXo4

Plugs after removal - photo attached


Seems like rattling comes from worn primary chain?


2. Compression test (hot) - made after idling test above on warm engine. Using kick start only
- dry test : 130/125/115/125
- wet test : 150/145/160/145

the same strange behaviour of cyl#3 observed during cold test (dry/wet)... what It could indicate? Rings issue?

Honestly I'm not sure about quality and capabilty of my tester, during kicking gauge arm is jumping up/down, see video from wet cyl#2 test
https://youtu.be/ROmpTSJdKIU

3. Before reassembling tank back, I left engine idling to burn oild from cylinders and raised idle - seems rattling is reduced / dissapeared. Smoke from pipes is white }condended water as enogine cooled down meanwhile)
https://youtu.be/lmlRuv11XtM

Note: I start to suspect something with coils/HT cables/plug caps (new in 03.2019) due to that irregular idle. Ignition is Boyer, so no points, no mech advancer

Anyhing else I should do before engine disassembly?
« Last Edit: October 25, 2020, 10:46:38 PM by Erny »
CB750K7 US model (1977)
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Offline deltarider

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Re: CB550K - engine rebuild (partial or full)
« Reply #25 on: October 26, 2020, 06:56:44 AM »
... even I felt during ride on low RPMs like engine running on 3cyl only occassionally... This is new behaviour to me. It feels like I ususally feel after bike washing (I did 1 week ago), engine does not rev more than 6k (feels like ign issue)
  Without having studied the rest of your post, this phenomenon is classic for a CB500/550. These bikes have always been praised for their overall reliability with one exception: plugcaps and plugleads especially in rain. Also: when was the last time you've checked the resistance there? You could start with checking the total resistance from one plugcap via the coil to the other plugcap. Realise that new resistor plugcaps are around 5kΩ each. The coils secundary itself is around 14-15kΩ, so with both plugcaps attached, you should read 24-30kΩ in total. When you read over 30kΩ in total, unscrew both plugcaps to be tested individually. Over time the plugcap's resistance tends to increase. When over 8kΩ, replace. Do not run and resistor caps and resistor plugs. When you have the choice, I'd prefer resistor caps over resistor plugs. Verify plugcaps are firmly connected to the wires and there's no arcing. Be aware this may occur intermittently. It's best seen in the dark.

Offline gbjeppm

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Re: CB550K - engine rebuild (partial or full)
« Reply #26 on: October 26, 2020, 08:47:19 AM »
Maybe I missed it, but have you checked your valve clearances and reset the cam chain tension yet?

After doing that to my CB550K it quietened down considerably.

Matt

Offline Erny

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Re: CB550K - engine rebuild (partial or full)
« Reply #27 on: October 26, 2020, 09:01:05 AM »
Yes I did. Several times. No change.
CB750K7 US model (1977)
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Offline deltarider

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Re: CB550K - engine rebuild (partial or full)
« Reply #28 on: October 26, 2020, 12:24:28 PM »
Ignition needs to be checked once more, as there's clear indication there is a misfire. You could do a simple RPM drop test by shorting one lead at the time. Do not just pull the cap whilst running, as the coil may not like it.* The somewhat darker plug, which # is it? About the primary chain noise, sorry, but I don't find it excessive. All CB500s I've heard, had similar @ idle. As long as noise vanishes under load, what's the problem? If you're going to undertake a renewal, I'll read your posts with interest ofcourse, but know that I have read (in the international forum) more than once that after renewal, owners had the noise reappear a few thousand kms later...
BTW, I love the sound of that repro set!

* Having seen Ashimoto's technical gear in his thread (Alladins cave) reparing his coils, I wonder what electronic parts one needs to build a device that can switch 4A at up to let's say 170 Hz. I'd like to build that, if it's not too expensive.

Offline Bryanj

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Re: CB550K - engine rebuild (partial or full)
« Reply #29 on: October 26, 2020, 01:03:55 PM »
Ask Ash, i am sure if he built it he will tell you

 

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