Topic: CB550 rocker arm shaft wear theory

[reddyvv]

Hi Folks,

Looking for some expert opinions on the following...

I am rebuilding a CB550K 1975 model which I've posted in the Project forum. I read many threads about the rocker shaft wear problem with these bikes so made sure to check my engine as well. Sure enough I have wear on one shaft but rather than the usual egg-shaped wear on the outside, the shaft decided to stay inside and that is where I detect some up-and-down play as the attached photo hopefully shows.

Now here is where my theory digresses from the conventional approach of sticking an o-ring into the end to prevent the shafts from turning.

I find that with the end cap fitted there is approx. a 2-3mm end to end free play of the two shafts. If one were to use an o-ring on the OUTSIDE end to push the shafts IN the outermost journal has the LEAST bearing surface compared to any of the other bearing surfaces. Which is exactly where my wear has occurred. However if I push my shafts OUT to butt up against the end cap those extra 2-3mm are making sure that the shaft fits snugly without any slop. 

So I suggest that instead of placing an o-ring at the end that an o-ring should be placed BETWEEN the two shafts so that the outer shaft can take advantage of the increased bearing surface at the outermost journal. Or maybe a hardened steel washer between the shafts and an o-ring on the outside to take up any slack?

***Note that the '75 has 8 short shafts whereas the '77 and later have 4 long ones so I can only speak to my case. I don't know if the '77 and later shafts are a little longer in total. If they aren't any longer then maybe they too should have a "stopper" on the inside end rather than the outside.

Thoughts?

EDIT: It's interesting that Honda went with the "lock the shaft" fix rather than drilling oil supply holes similar to the piston/gudgeon pin design. This would have allowed the shafts to rotate freely (a la gudgeon pins) with adequate lubrication rather than getting repeatedly hammered at the same rocker arm contact surfaces. Cost savings perhaps?!! Or a double screw up?!!

[dave500]

they get plenty of oil in them,its the rotation that causes the wear,so honda stopped them rotating.

[TwoTired]

they get plenty of oil in them,its the rotation that causes the wear,so honda stopped them rotating.

This.

Also, I don't think the designers expected the shaft to turn with the rocker movement, instead of the rocker upon the shaft.  Steel upon steel will wear far longer than steel against aluminum.

Care should be taken to keep any added orings from escaping the shaft bores and falling into the cam chain tunnel.  This is a safe bet when the orings are put at the end cap.

I had been toying with the idea that holes can be drilled and tapped to accept set screws from above which would not only keep the shafts from turning, but also force the shaft back onto the unworn bore base.  This would also restore the rocker position geometry.  For completeness, this would require two set screws for each rocker position.

This assumes I can't find a 77-78 pinned shaft replacement cover, to replace a worn one.

[phil71]

to play devil's advocate, I've worked on some pretty tired examples of this bike, and the extra play was never an issue as far as performance goes. In other words, it'll go till it doesn't, and you might be overthinking it a little. By the time it fails, it'll be two owners on.

[dave500]

or untill the tappet adjuster strikes its cover cap?the wear lets the rocker arm rise,its the upward spring pressure,the tappet runs close to the cover cap anyway,once its gone so far the tappet adjuster hits the cap,the engine will run fine and a novice may not notice the extra rattle?or have been told a little rattle in these old engines was normal even when new etc?and ride it into the ground?worst case the valve can lose lift,mostly inlets one and four,youll find the tappet has been way more adjusted down in these cases and lucky to have enough thread to lock the nut.

[TwoTired]

to play devil's advocate, I've worked on some pretty tired examples of this bike, and the extra play was never an issue as far as performance goes. In other words, it'll go till it doesn't, and you might be overthinking it a little. By the time it fails, it'll be two owners on.

Then you definitely have not seen the worst of them. 
But yes, they will still run a bit longer while in a failing condition.  However, the performance WILL suffer.

The shaft holes don't often wear evenly, with one side of an individual rocker shaft (1 of wearing faster than the other.  This tilts the rocker sideways along the shaft axis and effects how the flat of the rocker meets the cam lobe.  The tilt transfers all the pressure toward one end of the cam lobe and it wears both cam and follower rapidly, with galling easily seen.  If this issue is not caught and corrected early, the lobe wears down, the lift parameter reduces, and the cylinder progressively loses power.  Only a little at first, of course.

This, is in addition to the adjuster hitting the inspection cover.  Usually, by that time, the cam and rockers no longer meet service specs. either.

Frankly, I'm appalled that you'd suggest it perfectly acceptable to pass on known machine problems to owners later in time, even if hidden under the covers.

[phil71]

I've moved beyond being precious about these things. Spending thousands getting every clearance just right.. it's just insane. The bikes are not terribly valuable, and if it spends all its time in pieces on a  bench, what's the fun in it? When things like that start to happen, I often just source a good used motor (there are so many around). Rebuild it at my leisure while still having a running  bike, so I don't get sad on nice days.
 Also, I dont mean to say you knowingly pass on a lemon.. but if you want to be a real stickler, technically every engine is wearing itself out , and it's only a matter of time before something breaks. Sometimes, you just gotta let it go and have fun.

[reddyvv]

Thanks for the feedback, this is my first CB550 and it's good to hear opinions of those who've been around the block with these engines.

I agree with TwoTired that I can't just leave it be. Besides the fact that I've got it stripped down already I am seeing the early signs of some offset rocker arm shine starting to occur. Plus the tapping noise would drive me crazy now that I know what it is So I did a mock assembly of my cover with the orings "between" the shafts and the end caps on and I have zero up-and-down movement on the shafts. Moving the outer shafts to the outside fixed my particular problem so I'm going with it. I expect that once you get an egg-shape on the outside you are past recovery but if you are just starting to see some wear on the inside half of the journal I think my fix has some merit.

My project has 8300 miles on it and both the pistons and rings are within factory spec, nowhere near service limit. So I can't imagine the bike was pushed hard yet one rocker arm journal is worn down. In today's world I guess that would be grounds for a recall 

P.S. Although it's purely academic at this point in time I respectfully disagree about the shafts getting enough oil. Other engines have oil holes and oil grooves in the casings and haven't had what seems to be here a chronic problem.

[TwoTired]

P.S. Although it's purely academic at this point in time I respectfully disagree about the shafts getting enough oil. Other engines have oil holes and oil grooves in the casings and haven't had what seems to be here a chronic problem.

The thing is, there is really no need or desire to have the shafts turn in cover.  So, oiling is not really something that's wanted, as that would just make it easier for it to turn and wear.  The wearing surface was always intended to be the rocker on the shaft.  It just didn't work out that way in practice.  The oops was corrected with the pinned shafts of later design.

[xsmooth69x]

same thing happened to me

bad


good


nom nom nom the inside of my tappet caps


clickity clackity


put good cover on like this

[reddyvv]

Thanks for sharing those pics. Thankfully my worn rocker journal is just a little better than your good one!!

I found some interesting videos of a gentleman who had the problem with a CB500 and how he fixed it. They should be helpful for someone who is hearing that engine rattle and trying to figure out what it is. Should work for the 550s too.

The noise and the fix...

http://youtu.be/MDIkDb_HhKw
http://youtu.be/scqvEDH7zbU

Nice and quiet after the fix...

http://youtu.be/gDDK6ZOxmno

[scottly]

I had been toying with the idea that holes can be drilled and tapped to accept set screws from above which would not only keep the shafts from turning, but also force the shaft back onto the unworn bore base.  This would also restore the rocker position geometry.  For completeness, this would require two set screws for each rocker position.

I believe this idea merits further investigation. If someone wants to send me a worn out cover and at least one shaft, I would be willing see if it is feasible at a reasonable cost.

[RAFster122s]

Anyone got a picture of a 77-78 cam cover/tappet cover?  Sometimes the ebay sellers can't be trusted and the bikes may or may not have original parts on them these days.

What does the short 8 shafts look like versus the 4 long shafts. If the 4 long shafts are pinned, they won't slide out on their own, right?
What pins them in place? A screw?
Where can I find a part diagram showing the '77-'78 rocker arm & shaft setup versus the '74-'76 setup clearly?

Thanks!

David

[reddyvv]

The long shafts have flats on them that are contacted by 4 screws in the cover that prevent them from rotating.

[05c50]

What does the short 8 shafts look like versus the 4 long shafts. If the 4 long shafts are pinned, they won't slide out on their own, right?
What pins them in place? A screw?
Where can I find a part diagram showing the '77-'78 rocker arm & shaft setup versus the '74-'76 setup clearly?

http://www.partzilla.com/parts/search/Honda/Motorcycle/1975/CB550F+A/CAMSHAFT+%2B+VALVE+%2B+TENSIONER/parts.html

Illustration shows 1975 CB550 valve train, but the 77/78 shafts and pins are shown in the lower left corner

..........Paul

[flatlander]

I had been toying with the idea that holes can be drilled and tapped to accept set screws from above which would not only keep the shafts from turning, but also force the shaft back onto the unworn bore base.  This would also restore the rocker position geometry.  For completeness, this would require two set screws for each rocker position.

I believe this idea merits further investigation. If someone wants to send me a worn out cover and at least one shaft, I would be willing see if it is feasible at a reasonable cost.

i have a worn out cover and all the shafts. i'd be happy to donate them to research once i've gotten my hands on a replacement. will need to work out something for the shipping (i'm in the netherlands), otherwise just glad it will be used for a good cause.

[strynboen]

think drill the holes aut,,sentered so they are total lined up..then press steal bushings inn..and make it so the rotating are bloked..it all must be done in a tool machine..as un sentered holes are hard to drill aut..must use a 2/3 bladet endcutter heighspeed steel..and it can be hard to kontroll it in the mittel holes..vith a authang at 200 milimeters..eventuell made use" rival "to klean up..they are stabil but not specily stabil to hold korrekt senter

[RAFster122s]

Thanks guys for the pics and info links...much clearer but, I don't see flats and the screw for the shafts on my cover I picked ip. When they slid out I thought it was an early cover.

Thanks again!
David

[Krankyoptimist]

Wow.  I have my '76 CB550F apart at the moment.  Sure glad I saw this thread because my rocker cover has this spinning shafts issue.  I definitely want this fixed.  So I'm going to talk to a machinist friend about making me 4 new longer rocker arm shafts that I can pin. 
I have two questions left though:
1.  In the attached photo of one of my rockers that was on a canted shaft its obvious that this rocker is galled. I assume this is from it contacting on such a small patch. I find the pattern of galling bizarre, like termites, but anyway...is this rocker now trash or when I straighten out the egg shaped hole issue can I reuse since the contact patch will be re-spread across the whole face?
2.  If I have the new shafts made.  Will there be any issue with using the old rockers on the new shaft.  Seems like I recall metal doesn't like that kind of thing?

Comments/opinions appreciated!

[Trad]

I know this is a little bit of a plug but since this thread got bumped up again. I have two 78 cb550 rocker covers all with good shafts and rocker arms. If anyone is interested send me a PM and we can discuss price. Thanks.

[Krankyoptimist]

I wonder if those are identical to the 76 covers externally.  Except with the longer pinned shafts?

[Trad]

I wonder if those are identical to the 76 covers externally.  Except with the longer pinned shafts?

They are all identical externally from the cb550's to the 78 550. Only difference are the 4 long shafts and the wedge bolts which bolt under the breather.

[strynboen]

if somone in europa have some vorn ones..i like to try to fix it.


.if it goes vell vith the first..il can take more in my shop...but have to have a try on a broken one
to find if there are a realistic kvik and thep vay..to fix it proper..

[flatlander]

i do have a worn cover. am about to get a replacement and once i got it, the old one can be used to try fixing it.

[strynboen]

i have got one or 2,, 500 on my shop..the ovners dont vant me to do anything. (spend money).but they have the problem.
..adjusting the valve clerence..is imposibel.
.it gives some performance lost ..and gives a noisy engine

...i just let them drive mine total stock bike...and all says...waurv..you have tuned it great..lots of power..and fine heigh speed...

.the engine are fabrik spec.  this bikes run the ton easy..and have a nice power band..

..