Topic: CB550 Cam chain still driving me nutz!

[Jonesy]

I had a thread about adjusting the cam chain on my '78 CB550K. TwoTired made a suggestion of pushing the adjuster screw partway into the engine case in order to free it up (which I tried) and BryanJ sent me an informative document on pushing the kick starter pedal to ensure the chain was slackened on the tenstioner side, which I also tried.

I can't get the chain to quiet down. It's the loudest aspect of the motor. It comes and goes as I vary engine speed, but is usually present above idle speeds. It almost sounds like the upper half of the engine is full of marbles rattling around! The tensioner screw will only turn about an eighth of a turn in either direction before is stops. I've tried gently adding tension to it, but to no avail. It seems that no matter what I do, the noise won't go away and stays the same. The rest of the common engine noise sources (exhaust, intake, valves, primary drive and clutch) are all nice and quiet, so this sticks out like a sore thumb.

So, should I pull the valve cover and see if I can remove the tensioner and see if anything is wrong? Did these engines have noisy chains to begin with? Could it be something else in the valvetrain?

[cadler]

Have you tried adjusting it as it says in the manual?

[cadler]

if it sounds like marbles rolling around in your engine maybe it is not the cam chain, maybe you have loose hardware somewhere.

[Jonesy]

Have you tried adjusting it as it says in the manual?

Yep, that was the first thing I did.

if it sounds like marbles rolling around in your engine maybe it is not the cam chain, maybe you have loose hardware somewhere.

Quite possibly, although this sounds like classic chain noise as I've heard in in other Honda SOHC motors, just with the volume turned up. I tried wiggling the rockers around while I was adjusting the valves, and I did detect a tiny bit of side-to-side play (picture the way a bushing would slide axially along a shaft), but no "slop" as if it was worn. This variant of the engine had the rocker shaft wear issue addressed, so is there anything else I should be looking for or ways to diagnose?

[crazypj]

There is a possiblity that its just worn out. There is a rack and pinion adjuster for cam chain, if its moving eigth turn one way it should be possible to turn it at least one full turn the opposite direction (which would give maximum chain slack for dissassembly) if it isnt moving there is a problem. If the chain was previously over adjusted the tensioner blade probably has some deep grooves in it and needs replacing. pretty simple job on 550, only need to pull rocker cover and cam as far as I remember.
PJ

[crazypj]

I'm pretty sure you can use bent needle nose pliers to change the blade without removing the entire assembly.
PJ

[Jonesy]

pretty simple job on 550, only need to pull rocker cover and cam as far as I remember.
PJ

 I think it's a little worse than that if I remember. In order to get the tensioner out you have to lift the cylinders about an inch. That means at the very least a top end gasket set.

Well, then this might be a blessing in disguise, as the head weeps oil from both sides of the cylinders....

[oldfart]

The best tool/method for adjusting the 500/550 cam chain is the valve adjustment tool.  After loosening the locknut, use the screwdriver part to turn the screw c/clockwise and hold it in that position while you use the wrench part to snug up the locknut.  Worked when I was doing it for a living...

[Jonesy]

You turn it counterclockwise to tighten it? According to the crappy Clymer manual (came with the bike) it indicates that cclockwise will loosen it (I'd believe you over a clymer manual). This may be the root of the problem. I'll try it the other way tomorrow and report the results.

[TwoTired]

Something I've done in the past to quiet cam chain and a sticky tensioner.
With the engine running at idle, loosen the jam nut the put a screwdriver on the post and apply rotational pressure while listening to the cam chain noise.  This will give you feedback as to which way to turn the screw to reduce noise.  Make your final adjustment with the engine stopped and the engine positioned for chain slack at the tensioner.

It helped me, anyway.

Cheers,

[oldfart]

I would agree except that unlike most Honda SOHCs the 500/550 is best done engine running. 

[Jonesy]

Thanks, guys.. I thought about trying it while running, but wasn't sure about it. Coming from 2 of you, I now have the confidence to try it. As I said earlier, I'll let you know how it goes.

[TwoTired]

Perhaps I should clarify.  While the engine is running, I will aid the tensioner spring by applying rotational pressure to the stud/post to quiet the chain.  I then remember how much tension I added, stop the motor, position the crank for chain slack, reassert the rotational pressure learned previously on the stud and lock down the jam nut.  I don't know if the extra step is actually needed.  I just think that a stopped cam chain will exert less pressure on the tensioner than a moving one.

The method hasn't gotten me in trouble so far...

Cheers,

[Jonesy]

Thanks to TwoTired and Oldfart, the CB550K purrs nice and quietly!

It turns out (no pun intended  ) that the Clymer manual had me setting the chain very loose. As soon as I loosened the locknut, it quieted down instantly. I gently turned the adjuster screw until I found the quietest position (too far one way would bring back the loud chain chatter, the other would be the loud whirring sound of the chain riding harder against the tensioner slipper) and cinched it down. Another problem with a happy ending. 

If we still had Karma I'd give points to each of you and wait a half hour and give you more! (I'm that thankful!)

The bike is pretty much set now. Got some minor inconvenience issues (the warped speedo faces, which ElCheapo was hoping to make replacements for and the weeping oil from the head, which can wait until winter...) but the big stuff is fixed. My wife has started riding it and she likes so much more than her old CB360. We can go for a long ride and her hands don't get numb from vibration fatigue!

[oldfart]

Cool!  Appreciate the followup. 

[putnaja1]

Thanks to TwoTired and Oldfart, the CB550K purrs nice and quietly!

It turns out (no pun intended  ) that the Clymer manual had me setting the chain very loose. As soon as I loosened the locknut, it quieted down instantly. I gently turned the adjuster screw until I found the quietest position (too far one way would bring back the loud chain chatter, the other would be the loud whirring sound of the chain riding harder against the tensioner slipper) and cinched it down. Another problem with a happy ending. 

I gotta ask- how quite is quite as far as the cam chain goes?  I can hear mine, but it isn't really really loud- it is present and audible.  Is this normal?  Should it be un-noticable when running/idling?

[TwoTired]

Well, it's a smaller version of your drive chain.  But, it moves faster, and some of the noise is blocked by the engine case.  However, it is always rubbing on the chain tensioner.   And, that noise it transmitted directly to the engine block.  You're gonna hear it. If it is louder than your drive chain at 50 MPH, it's too loud.

Cheers,

[jph550]

This has been a great post!

I'm getting excited to do my first tune up on my '76 550K. I know this is something I would have to address sooner or later and now you've helped me along.

Worthy of putting into the faqs page ;D1


Jonesy, glad you didn't have to tear into the top end

[volthause]

So counter clockwise to tighten the tension? Interesting (but not surprising) that the clymer would have it wrong.

I've been needing to do this as well as a general valve lash adjustment. Thanks for the info!

[Jonesy]

Thanks to TwoTired and Oldfart, the CB550K purrs nice and quietly!

It turns out (no pun intended  ) that the Clymer manual had me setting the chain very loose. As soon as I loosened the locknut, it quieted down instantly. I gently turned the adjuster screw until I found the quietest position (too far one way would bring back the loud chain chatter, the other would be the loud whirring sound of the chain riding harder against the tensioner slipper) and cinched it down. Another problem with a happy ending. 

I gotta ask- how quite is quite as far as the cam chain goes? I can hear mine, but it isn't really really loud- it is present and audible. Is this normal? Should it be un-noticable when running/idling?

It's very obvious if you perform the adjustment while the bike is running. It only takes about an 1/8th of a turn in either direction to go from one noise extreme to the other. Loose chain make a chattering sound, while too tight makes a distinct whirring noise.

[lovecrusher]

Hmmm, I noticed during the initial tune up that the tensioning screw turns completely free in both directions with no stopping.  Since I haven't got the carbs back on it yet, it hasn't presented itself as a problem yet.  However it sounds as if it might this weekend.

I have a hard time envisioning how the tensioner works with the tensioning screw for some reason....  Why would my tensioner screw freely turn in both directions like that?  Any ideas?

Also, do you all know of any aftermarket tensioners for the 550?

[Jonesy]

I would venture to guess that your might actually be moving freely, as these tend to gum up over time.

The tensioner has a curved leaf spring with a rubber/teflon coating (referred to as the "slipper") that rides against the slack side of the chain. The ends of this sping are attached to metal slides that have gear teeth on them. The tensioner screw is attached to a small gear between these metal slides. When the tensioner screw is released, the spling will tension itself and the slides will move accordingly. When you want to slacken the chain, turning the srew (and gear) will move the ends of the slides farther apart, trying to flatten out the curved spring and pulling it away from teh chain. Moving the screw the other direction pulls the slides together, causing the slipper to bow outwards more, pushing harder on the cam chain.