Topic: New CB550K3 beauty with strange sound from engine (solved)

[jensk]

I have just bought this beauty from Germany. Not many - if any - like it available in Denmark where I live.

When I saw the ad I just had to have it. Along with it came tankbag, extra new original tank - the one on the bike has a dent, toolset, owners handbook, original buyers receipt, extra original saddle with ripped vinyl, chrome luggage carrier and a lot of other extras. The only minus is that the exhausts is beginning to rust. One exhaust has a patch over a hole so I will have to change them within a couple of years.

When the bike arrived it started easy and idled well. There was a snake in paradise - a strange sound that I have never heard from my other CB550. It is a clacking/hammering sound like some part of the engine is hammering on some other part. The sound follows the rpm's. It get more intense as I let the bike pull - I am very carefull not letting it pull to much. If I have the engine breaking the hammering almost disapears.

I checked valves, camchain, ignition, plugs, synched carbs but it didn't change the hammering/clacking sound from the engine. It sounds like it is comming from the bottom part of the engine and not from the head.

I dumped the sump to look if there were any parts in there. It looked like the engine was build yesterday and no ripped of part of metal in the sump. I took of the clutch house to se if I could se anything wrong there. I took a lot of pictures from underneath up in the engine and of the clucth.
Pictures can be seen here http://www.cig.canon-europe.com/a?i=1wlBZHDpp7

I checked if it was the main drive chain but it seems like it is in good condition and that it is not able to touch any parts of the engine (housing or oil galleries) except the intented wheels.

I fear that the clacking/hammering means that I will have to split the engine completely. Could someone on the forum please help me diagnose this sound so I can get this beauty  out on the roads with all her shining chrome and 4 exhausts with me in the seat.

I have supplied 2 videos of the clacking/hammering
http://www.kjellerup-hansen.dk/nr17/film/MVI_0412.AVI [7 Mbyte]
http://www.kjellerup-hansen.dk/nr17/film/MVI_0413.AVI [17Mbyte]
/jk

[SOHC steve]

Congratulations on your new bike,it looks fantastic. I have never had a 550 engine apart so I cant really offer anything other than general ideas,I listend to the videos and combined with the fact that it varies with engine load I would have a good look around the exhaust pipes for a crack or holes.They can make weird noises,much like a loud tappet and certainly changes under load.The engine looks REALLY  clean,but may be worth checking oil pressure and also dropping the ignition leads off one at a time to see if the noise can be tracked down to a cylinder or if it reamains constant then it is in the box somewhere I guess.The lack of metal in the sump really makes me optimistic ,hopefully this will help some,good luck!

[OldSchool_IsCool]

Beautiful bike!  Congrats on the find!

Have you looked for rocker shaft wear?  I'm not sure which 550K's had the problem, but year wise, I believe they were '76 and older.  Here's a thread on the issue:

http://www.sohc4.us/forums/index.php?topic=20408.msg231208

[jensk]

Thank you for the replies. I have remounted the sump and clutch housing, topped of with oil and started again. The clacking still there. Listen to new and better recording where you can hear the clacking very clear.
http://www.kjellerup-hansen.dk/nr17/film/MVI_0461.AVI

I have tightened the exhaust headers and checked if the sound came from the patch that is on one of the exhausts. It doesn't.

I have pulled the plug one at a time while the engine was running and the clacking kept on independently of the plug pulling. Clacking follows engine rpms.

Clacking is only there when engines idles or is pulling. If i use the engine as a brake (let go of throttle while driving) the clacking is gone until i pull the throttle again.

The sound definetely comes from either the crank or the clutch/gearbox. It sure would be nice to have an opinion on what this might be. If it is dangerous for the engine - like eating oil galleries etc.

My only other alternatives is to go to a Honda dealer or pull the engine apart myself. Me pulling the engine apart isn't a guarantee for success since i haven't seen these engines inside before - so how do I identify an error 

[Tvag]

Hey nice bike buddy. I hope someone can give you a hand diagnosing this problem in your engine. I'll keep an eye on your progress.

[Glenn Stauffer]

Are you sure it is from the bottom of the engine?  I had a problem on an engine and it turned out to be the tappet screw set out too far causing something to hit either the tappet cover or the head - forget which now.  But, it made quite a racket.

I've never heard the sound from bad main bearings on an SOHC/4 engine, but I always figured that to be a deeper sound.  Whatever it is, it ain't good as we say over here.

Different areas will sound off at once per rev or once every other rev or some other fractional sequence; maybe you can put a timing light on it and get your eyes and ears working together to help you focus in on the problem area.  No sense tearing things apart further than makes sense.

[TwoTired]

I just found out my new computer will play AVIs!

I think you are right not to operate the machine with that noise.

To me, it sounds like intermittent gear dog interference in the transmission, or perhaps a broken/ cracked gear.

If the former, you should be able to find a gear selection where the noise disappears.

Note the noise under the following conditions:
- Clutch in / clutch out.
- On center stand, clutch disengaged, try all gear selections.  Are there any where the noise goes away?

Does your clutch disengage completely?

If you can find a gear that selection where the noise goes away, then perhaps you have a bent/worn shift fork or shift drum issue that does not center the dog sliders between engagement slots.  The clacking would be the slider dogs hitting the slots.  The noise would go away when the dog was fully engaged.

If it happens regardless of gear selection, then I imagine main gear meshing issues, loss of gear teeth or foreign matter lodged between gear teeth.

I suspect you will have to remove the engine and separate the lower case to correct the issue.  Pity, as the bike looks like new.

I've got a parts bike in the back yard that makes similar but louder noises anytime the engine is run.  I bought new transmission guts for it.  But, it is yet another back burner project in waiting.

My condolences. 

[jensk]

I am sure the clacking doesn't come from tappet screws hitting tappet covers since I had all the tappet covers of while engine was running and clacking 

I have gotten a mail from PO. He says that the clacking definately wasn't there when the bike left his place. The bike was picket up by a bike transporter that i contacted. PO seems very serious and has taken good care of the bike so i tend to believe him when he says that it was free of errors when it left his place. If that is correct the fault must have emerged during the transport. Transport was over several days with the bike being loaded from one truck to another by the transporter. Can reloading pulling bike from one place to another have harmed something inside the gearbox or the crank?

I will try Glenns suggestion with the timing light - if I can get my ears synched to my eyes  Then maybe I can figure out if the clacking is one clack per crank revolution or one every other.

<out in the shop testing>

I have tried Glenns suggestion. The clacking follows rpms. I tried to count clacks at 1400 rpms - I counted approx 180 - 220 clacks pr. minute.

TT I would like to say: Your condolences not accepted - but who am i to ....

It clacks throught all the gears. I tried all gears on centre stand with footbrake as load. It clacks with clutch pulled and not pulled. The clutch seems much better than the clutch on my existing CB550 (it needs new clutch platres) so my guess is that the clutch is ok. gear selection is very easy also finding free gear.

If there was broken gears I should be able to se broken of parts in the sump or Sump was absolutely clean when i had i off today.

It sounds like when rpm's get below 1000 the clacking stops or gets more intermittend but it is hard to hear because the engine starts running very uneven.

[kslrr]

This is a question for TT to help figure this out.

Could it be one or two cylinders running rich combined with carbs not synced?  Though you would think it would clear up in the higher RPM's.

Answer to jensk.  I can't think of how transporting the bike would knock something loose inside the engine.

[jensk]

I wouldn't imagine that transportation in vans could harm the internal of these sturdy machines but my alterntives are one of two:

Either the PO has sold me the bike with this error or the transporter has been using the bike and harmed it using it.

It was 6 days under transport due to weekend and hollydays.

[bistromath]

Well if the noise disappears under deceleration it is probably a bottom end/transmission/clutch problem, rather than top end as was suggested earlier. If it were a top end issue it should still be present during deceleration.

If you hear it with the clutch engaged AND disengaged, well, it's not a transmission issue, is it? This would point to crank, main bearing, primary chain or clutch damage.

Check for good oil pressure. The oil pressure sender is not always reliable. Does the red oil light come on while the ignition is on before starting? Does it go off as soon as the bike is started?

[jensk]

Check for good oil pressure. The oil pressure sender is not always reliable. Does the red oil light come on while the ignition is on before starting? Does it go off as soon as the bike is started?

Oil pressure seems very ok - lamp goes out emediately after start - turns on again after engines stops. When i started the bike with tappet covers off it started spraying oil out of the tappet cover holes after a minute or two.

It sounds like I have to get the engine out of the frame and have the bottom half off.  So much for driving through the comming indian summer on this beauty

I haven't been inside any of these engines before - read it is 35 years ago i last build up an engine and it was a onelegged Matchless 500 from 1953. Can I replace ie. the main drive chain by just opening up the bottom or do i have to dismantle the entire engine?

How do I indentify the parts that is causing this error

[TwoTired]

This is a question for TT to help figure this out.

Could it be one or two cylinders running rich combined with carbs not synced?  Though you would think it would clear up in the higher RPM's.

All the gear clack I've encountered due to carb imbalance went away when the engine was revved up.


I don't know what the problem is jensk's poor bike.  But, here is something you may consider trying.

Take out the spark plugs to relieve compression.  Select top gear and rotate the crankshaft through several revolutions using the rear tire while on the center stand.  Can you pick up a noise or feel any change in feel while doing so?

You could also use the kick start lever with the trans in neutral and feel/listen for something odd.  This will probably only be helpful if you do feel/hear something.  And tell you nothing if there is nothing discernible.

(sigh)
I'm going to paint you a horror picture.  Feel free to reject of you chose.  I once had a gear train where a gear cracked from tooth valley to the shaft core.  What this did was widen the tooth spacing where the crack occurred and in operation made a tick sound each time this tooth section engaged it's mate.  The tick sound varied with the load and load direction of the engagement teeth.  The crack in the gear eventually widened to where the teeth would no longer engage, jamming up the works.  This occurrence was NOT in a CB550 motorcycle, or even a motorcycle, for that matter.
However, if something similar has occurred in your bike, the gear mesh tolerances and the changing rotational forces could make such a malady sound like an intermittent clack and would vary with engine speed.  I'm just sharing thoughts here.  It is not a diagnosis.  I'm just trying to match up the noise with parts inside the engine/trans. 

Can you localize the sound source with a screwdiver tip contact and the handle placed in your ear socket?

Cheers,

[Glenn Stauffer]

TwoTired is right - take the time to try to isolate the cause of the sound before you start ripping things apart.  Get a mechanic's stethoscope (http://www.toolspot.co.uk/product/mechanics-stethascope) and use it to try to pin-point the area of the engine that is the source of the sound.

I have a hard time believing this sound wasn't something the previous owner knew about since I can't think of a scenario where transporting the bike could cause such damage to the the engine. 

Though maybe it is not mechanical at all, but caused by fuel or spark - as twotired suggested, try to 'feel' the cause of the noise without the engine running.  If a bike was subjected to some rough treatment in transit, something could have shaken loose.

[jensk]

It is allmost midnight here now so first thing tomorrow will be feeling the error - with no plugs in the engine. After the feeling session i will try to listen - with engine running.

The clacking i definately not due to non synched carbs. I have heard that sound. Besides i synched the carbs this morning
The result is here

Thank you for all the replies.
/jensK

[Bodi]

Listening to the sound I would have a long hard look at the exhaust connections. The sound is pretty slow compared to the engine sound, like it's at one cylinder firing speed. Moving the bike could give the exhaust system a good whack or maybe a holddown strap pulling at it. Getting louder on throttle and disappearing on coasting suggests exhaust as well. Big end bearings make quite a loud noise at engine RPM speed, they change a bit with throttle especially when just developing but that doesn't sound like it to me... been wrong many times though!

[jensk]

Bodi I have done the best i could listening to the exhausts but couldn't locate the sound to any of them. When i pulled the plugs one at a time while the engine was running. None of pulling plugs made the clacking disappear. On basis of this test i have ruled out the head or exhausts as cause for tthe clacking.

I have heard from PO. He suspects the clutch basket or rather the teeth on the back of the clutch basket to be loose or displaced. He writes that some of the rivets holding the toothwheel on the back of the clutch basket once broke of and that he many years ago had it riveted back on the basket. Po describes it as:

"I remember the first year i had the Honda, i´ve got a problem with a noise
nobody could locate. In the end it was caused by a brocken gear of the
clutch-basket. This gear is fixed with rivets on the basket an this gear has had  a
crack. No big thing, but hard to find."

I guess that i have to replace the clutchbasket with a new one. Funny though the clutch seems to work excelent - or maybe im just acustomed to my old worm clutch with warped plates on my other CB550.

I am away on business trip but when i'm back for the weekend I will replace the clutch basket.

[jensk]

Error found. A tooth had broken of on the toothing on the back of the clutchbasket. I took the clutchbasket from my other CB550K and mounted it - and the clacking sound was gone. I haven't been able to find the missing tooth - neither in the sump nor in the clutch housing. Do i have to worry about this or

I wonder how this could happen during transport from Germany to Denmark . It was a route of 1600 km. The transporter said he had to have a couple of days of as he had been driven for 10 days 12 hours a day. I wonder if the spare time during his 3 days of was used driving the bike and driving it to hard thus ruining the tooth?


Thank you for all your responses to help me solve this issue.
/jensK

[kslrr]

When you closed the deal with the seller, did he indicate the current milage?  If so, that would be proof.

[jensk]

I have a picture of the instruments taken by PO. The photo show that the bike hasn't been running between it left his place and it arrived at mine. This indicates that error was there when PO sold me the bike.

What really worries me is where the missing tooth is because i haven't found it in the sump or in the clutch housing. I guess that a piece of metal this size running loose around in the motor (crank or gearbox) could make a lot of damage to other parts of the engine.

[kslrr]

That chunk of gear tooth would most likely be too heavy to be moved by the flow of oil.  Maybe it became wedged into a crevious in the clutch housing when it was thrown from the gear.

[jensk]

I must have a better look next time I have the clutchhousing of. It will be next weekend when I will have a second check of the torque of the bolts holding the clutch springs.
/JK