Topic: 77 CB550K Excessive Noise -- Unsure if Cam Chain, Rocker, or Primary Chain?

[Maraakate]

Hey everyone,

I was riding the bike today and while idling in traffic I heard a bit of noise coming from the engine.  I gave the throttle a blip and it went away.  Rode for another 45 minutes, never heard the noise again.  When I got to the next stop I noticed a bit of smoke coming out of the exhaust on that side.  When I got home I restarted the bike and the noise was back.  I took the tappet covers off and noticed a lot of side play on Cylinder 4 for the Exhaust Valve.  Is this a bushing that is worn?  What do I need to do next?

Attached is some videos

http://maraakate.org/cb550k/20200811_181302.mp4
http://maraakate.org/cb550k/20200811_181552.mp4

EDIT:

Since I am no longer certain of it being the rocker I have updated the thread title.  To save some time for others reading I am unsure if this noise is from the Cam Chain, Rocker or Primary Chain (or elsewhere).  It is definitely internal and is louder on the right side of the bike as opposed to the left side.  Unsure if it is coming from the center.  Unsure what the next step is in diagnosing the issue.  Noise is there between all RPM ranges.

[bryanj]

Exact model of bike would help, there is no adjustment for side play on rockers but early camcovers can wear the spindle holes

[Maraakate]

It's in the topic, but 1977 CB550K (USA model aka CB550 "Four" K).  Which is why the noise is strange to me because from what I have read here that problem was fixed with that year.

The only other thing I could think of is a valve is really loose?  I can check tomorrow after the bike cools down.  I did the valves not too long ago, maybe about 2000-3000 miles about 3 months ago.  It's about due for a check up, but I doubt it got that loose that fast.  And when I popped the covers off none of the nuts were loose on the adjusters.

Another possibility is the cam chain(?) I tried readjusting it per the service manual with Cylinder 1 rockers loose and that whole 15 degrees past the T mark with the advancer peg.  Made no difference.  However, I did note when I loose then the 10mm nut on the adjuster the adjuster bolt itself (with the slot for a straight screw driver) moves with it.  Is this normal behaviour?  Maybe this is part of my problem?

The sound is definitely coming from the center and/or cylinder 3 or 4.  It's loud as day on that side of the bike but quiet on the left side of the bike.

Just for reference this is the version of the cam shaft, etc. I have: https://www.partzilla.com/catalog/honda/motorcycle/1977/cb550k-a-550-four-k/camshaft-valve

[Maraakate]

The noise in this video

is practically the same noise.

In his video he states in a comment that the fix was: "it was a carb sync issue combined with the cam chain tensioner. Valves were gapped but the other issues were the main culprits. Bike has been sold".

The carb isn't dead-on synced.  But I didn't think it would make THAT much of a difference if it isn't dead-on.  I haven't checked it in over a year.  Maybe it has drifted?  But I do think that maybe it could be related to the cam chain.  But that comes back to the issue I mentioned earlier.  Which I can take a video of tomorrow on how I adjust it, maybe I am doing something wrong or the tensioner has issues and I have no real idea how to diagnose the issue specifically.  And on that note, BryanJ has mentioned a flat rate way he adjusted the tensioner.  I'm assuming he did this if the bike was hot or cold, so I assume the bike being dead cold to adjust the cam chain makes no difference?

[bryanj]

I never read titles and rely on info in question, yes i am a crusty old fart but then thats me.
It ought to have the modified cover but that could have been changed in the past by a po.
I never play vids as i dont have the bandwidth and have had too many virus probs.
Never understood this particular way of adjusting camchain the dealer workshop way as intructed by Honda UK ech support was to loosen adjuster, put weight on crank so its just about to turn then all slack is in rear run of camchain and whilst holding nip up locknut/bolt. This works for all the sohc fours

[Maraakate]

I suppose.  Is there a way I can tell if the cam chain is loose?  I.e. can I loosen the top inner cover and pull on it for slack, or start the engine (briefly like 5-10 seconds) and see if it's pretty sloppy in it's movement?

I'm starting to get a gut feeling it's something with that tensioner.

[Maraakate]

Other thoughts as I think more about this... the primary chain?

The more I think about this, the loose rocker side-to-side play is apparently a normal thing at certain parts of the stroke and my bike is the year this problem was fixed so I no longer suspect this.

How do I check to see if there is a problem with the cam chain and/or the primary chain having too much slack?  Classic screwdriver against the ear didn't really help me isolate anything.  Bike has about 25,000 miles on it.  I got it with 18,000 miles and have been riding it for a year.  Bike has ran extremely well up until this incident.  Oil has been changed multiple times, I use the Honda GN4 10W40 and get the proper oil filter from the dealer, so we can rule out maintenance neglect.  At least from me owning it.  I would say after 6-8000 miles all me in the past year any issues like that would have popped up by now so I am guessing it's from one of the two internal chains with general wear from the parts being 40 years old and the fact the bike sat unused for 20 years.

[bryanj]

That mileage at that age both chains are shot, but only need replacing if you have another reason to strip the engine

[Maraakate]

Okay, but how do I specifically tell which chain is making the noise?

Yes, looks like cases will need to be split which sucks.

The top end has had a small oil weep at the head gasket, so this would be an excuse to fix that while I am at it.  Seals are fine, but I would have to replace those too to do this job.

[Maraakate]

I called a local shop that has been around since the 60s that knows how to work on these bikes.  He said the tensioner is probably OK, but to pull the pan and see if theres an rubber bits, etc. floating around in there.  I pulled the pan and everything looked OK.  Some small sludge at the bottom, but nothing extreme.  I looked up there with a flashlight and didn't see anything funny, actually looks very clean in there.  Gears looked good too.  Primary chain has a bit of slack and some side play, but I think it's probably OK.

The shop also said that considering the amount of miles I put on it (about 6,000 in the past year) and the relatively low miles (25,000) that the Primary would have progressively worn out, and he said that pulling in the clutch will change the noise as it's starting to wear, typically anyways.  So he said he was pretty doubtful it was that.  I tend to agree, considering the noise is incredibly loud and clearly from the right side of the top of the bike.

I bought a proper mechanics stethoscope and the noise seems the loudest on the exhaust flange for cylinder 3.  While I was at it, I checked the valve clearances and they have drifted a little bit, but nothing seemed way out of line.

At this point, I guess I have to pull the head off and see what the deal is.  Not sure why I am having this issue; I was pretty good about changing oil, checking its level frequently to learn how often it needs topped off, and things of that nature.

Will keep everyone posted when I finally get around to pulling the head, as I will need to arrange having it stored somewhere in order to leave it in that state.  I'm guessing I'll probably have to take it to a shop to have them check the tolerances if I see nothing obvious.

[scottly]

I bought a proper mechanics stethoscope and the noise seems the loudest on the exhaust flange for cylinder 3.

Exhaust leak? Try taking a length of rubber hose and holding one end next to your ear, prob around with the other end; it's the best method I've found for locating exhaust leaks.

[Maraakate]

I bought a proper mechanics stethoscope and the noise seems the loudest on the exhaust flange for cylinder 3.

Exhaust leak? Try taking a length of rubber hose and holding one end next to your ear, prob around with the other end; it's the best method I've found for locating exhaust leaks.

By the other end you mean the intake side?  Yes, I can hear it, but it's not as loud.  Seems like finding noises with the stethoscope is a bit of an art.  I've noticed the sound can be heard practically everywhere on the top end with the scope, but it's significantly louder and comes in with "clarity" (if that makes sense) on that exhaust flange.  The sound sort of sounds metallicy, in the higher pitched range, when the scope is on that area.  The only real way I can describe.  I could try to record it, but trying to get some small mic to fit into the stethoscope ear buds may be difficult.

Really though?  Exhaust leak now?  Wouldn't I feel some air pressure being pushed out around that area in an obvious way or no?  Do those gaskets just simply go bad after a while for no good reason?  Would pushing on the pipe (with some good leather gloves of course) change the sound?  I kind of figured an exhaust leak would a really loud low end note.

I did actually check the pipes and headers themselves and none of them have holes.

http://maraakate.org/CB550K/20200812_125604.mp4  -- Here is a new video of just the noise as the bike is running and how it matches with the revs if this helps.

But maybe you are on to something.  I personally think the noise sounds like it could be valve or cam chain trouble... but, I did take it a quick trip around the block and the performance of the bike is the same as it's always been.  You would think there would be some progressive loss of performance with this kind of noise.

[evinrude7]

can you isolate to one side of the motor?  pull the tappet covers off and see if there are any distinguishing marks on the underside of each cover. 

[Maraakate]

I did take the tappet covers off and I didn't see any marks or chunks on the under side of them.  It does really sound like some kind of valve train noise though.  And yes, its really obvious on the right side of the motor on the top end.

[Maraakate]

I bought a proper mechanics stethoscope and the noise seems the loudest on the exhaust flange for cylinder 3.

Exhaust leak? Try taking a length of rubber hose and holding one end next to your ear, prob around with the other end; it's the best method I've found for locating exhaust leaks.

You may be right scottly!  Just a few moments ago I put oil back in the bike, started it up and sound was still there, but as it was warming up I tightened up the exhaust studs and on cylinder 3 and 4 they were kind of loose.  Not enough that they were rattling, but they had a good quarter-to-half-turn left in them, so maybe they worked their way a bit loose.  I decided to take it for a small ride with the continuing noise, verifying performance is still the same as it's always been.  After I got a block or two up the street the noise stopped.  I drove it around for 5 minutes around the neighborhood.  Parked it, put it on the centerstand, checked the oil level, and started it again and the noise was still gone.

I would assume if it really was an exhaust leak that means what I've done is probably a band-aid and the gasket is just going to give me the same grief again in the future.  When I replace the crush gasket, do I need to replace the collars as well, or just the gasket?  Considering these parts are cheap, and studs are still available this might be a worth while cheap part replacement to verify if that was the issue before I start ripping the top-end apart.

While I was at it, I did check the 10mm's on the intake manifold, which were good already.  I knew as much because I redid the o-rings last year and torqued it to spec.  I checked the 10mms on top of the valve cover and they were good too.  The only things that had a bit of adjustment were those exhaust studs on 3 and 4.

[bryanj]

Just the crush washers settling down, you wouldnt be the first to have chased a loose tappet when an exhaust was not quite tight

[dave500]

a proper vacuum sync does really help,be sure the ignition is squared away first though.

[Maraakate]

Just the crush washers settling down, you wouldnt be the first to have chased a loose tappet when an exhaust was not quite tight

Interesting.  I will order some new crush gaskets.  But like I said, what about the collars?  Are those "consumables" as well?

a proper vacuum sync does really help,be sure the ignition is squared away first though.

The ignition is squared away.  I recently set the points gap, set the timing with a timing light, and lubed the cam and felt about a month ago.  I just came back from a long trip two weeks ago and before I left and when I reached my destination I reapplied some lube on the shaft.

[Scott S]

 Have you checked the valve adjustment since the noise started?

[Maraakate]

Have you checked the valve adjustment since the noise started?

Yes, that was the first thing I did.  I rechecked it the next day after it cooled down and sound was still there.  I've already set the valves twice in the past year.  I usually just do them at the start of a season.  They drifted a little bit out of spec but it wasn't anything obscene.  And yeah, after I set them the noise was still there.

[Maraakate]

Took it for a ride this morning, noise is still gone.  So maybe it really was the exhaust gasket.  Still need to know if I should just replace the gaskets or do the collars need to be replaced when you do the gaskets?  I really don't know as I've never had to do it before.

[bryanj]

Just gaskets BUT if noise gone dont need it

[Maraakate]

Just a post-script to this, bike is still running fine after tightening up those exhaust flanges on 3 and 4.  Thanks for the help!