Author Topic: Cb500 Rocker Shaft Upgrade (Read 2343 times)

ben.cb500 · « **on:** May 17, 2011, 11:05:58 AM »

read through this article

http://www.motorcycleproject.com/motorcycle/text/headgask.html

Quote

If you have a 1971 through early 1976 500/550 whose engine number is under those mentioned above, it has a rockerbox whose rocker shafts rotate while the valves open and close. This is an oversight in design that leads to prematurely worn rocker shafts and rockerbox. A kit was made available back in the old days which locked the shafts to the casting. There is a much easier fix however. Take the extra four cam end-cap o-rings you purchased. After removing an end-cap, place one o-ring in each rocker shaft hole, up against the shaft, then reinstall the end-cap. When the end-cap is reinstalled, it will compress the extra o-rings against the shafts, and keep them from rotating.

so what it is saying is place an oring between the dowel pin on the end caps and the rocker shaft? I have mine apart and the shaft floats into the center of the head as well, where the cam chain hump is, whats to stop it from just moving that way?

Whats the percieved benefit?

TwoTired · « **Reply #1 on:** May 17, 2011, 11:28:16 AM »

The shafts do not normally reach all the way into the chain tunnel. They are limited in their inward travel. If yours have worn through, the cylinder cover needs replacement.

Normally, the inward travel is limited, but the shafts are free to rotate, which can wear the cover shaft bore holes oblong. This ruins the geometry and screws up the cam lobes and followers. If the bore holes have not yet worn badly, the added orings help hold the shafts in place so the rocker pivots on the steel shaft rather than the shaft turning against the soft aluminum of the cover.
I know of no long term studies that prove this. Though I have added orings to shaft ends in hope that it will extend the cover life of a brand new one I installed ($255). It made the installation of the end plugs difficult, the result of squashing the orings between end plug and shaft.

Cheers,

ben.cb500 · « **Reply #2 on:** May 17, 2011, 01:16:28 PM »

...interesting, as the shafts on mine do 'fall' into the middle of the aluminum cover.....i do have a spare, will compare and post an image tonight...

TwoTired · « **Reply #3 on:** May 17, 2011, 02:03:25 PM »

The newer upgraded cylinder covers use just 4 rocker shafts total, which are pinch pinned, locked, into place. The early covers use 8 short shafts, which are free to spin.
It's possible for people to mix up parts in a haphazard repair attempt to fix the oblong bore hole issue.

I don't recall checking the new style cover to see if the shaft bore hole goes into the cam chain tunnel.

ben.cb500 · « **Reply #4 on:** May 17, 2011, 02:05:27 PM »

Took some pics of the two rocker covers,

FIRST 2 PICS
the original off a 71, the shafts are open ended. looks to be as per factory with some light wear.

LAST 2 PICS
the other of unknown year but a 500, is completely closed in.

I am leaning to just reinstalling the original, but if anyone can comment on what to look for wear wise I would take a closer look for sure...

thanks

dave500 · « **Reply #5 on:** May 17, 2011, 02:36:03 PM »

heres the improved later type,these dont go all the way through as the holding bolt is in that area,ill have a look later at another motor i have with the older type on it.

if you do get the late type dont over do the tapered lock bolts,itll crack the cover.

TwoTired · « **Reply #6 on:** May 17, 2011, 02:44:47 PM »

For the wear issue:
http://forums.sohc4.net/index.php?topic=20408.msg212239#msg212239

I looked at all my covers. They are from the 550 and have a different cast than your "early" style. They all have holes through to the tunnel on the bottom of the covers. But, the holes are smaller and DO NOT let the shafts through on the inner side.

I'll attach another pic of the wear viewed from the inside.

ben.cb500 · « **Reply #7 on:** May 17, 2011, 03:32:55 PM »

...so I gather from above that there actually 3 designs floating about?

1st iteration, open into the breather cover area
2nd, closed into the breather cover area
3rd, closed with retaining bolts drilled through area

this sound right?

TwoTired · « **Reply #8 on:** May 17, 2011, 03:39:15 PM »

It would appear so.

...that we know of...

Greggo · « **Reply #9 on:** May 17, 2011, 04:00:31 PM »

Interesting.

Hannibal Smith · « **Reply #10 on:** May 17, 2011, 04:16:05 PM »

I have a '74 and it has closed breather area, but 8 separate shafts "free spinning".
Engine number CB550E-10212**

I used 2 thin o-rings stacked per shaft allocation, and the side covers bolted down nice and snug without any gaps. If everything is getting proper lubrication, hopefully minimal pressure is required to prevent rotation- For what it is worth, my motor had 24,000 on the clock, and the rockers/shafts were darn near perfect without any wear/ovalization in the casting bores, just a perfect no slop install when I rebuilt the mill. I would not even know this might be an issue if the Forum had not brought this to my attention, so my motor appeared to be doing just fine with the "old" style shaft system-

Hannibal Smith · « **Reply #11 on:** May 17, 2011, 04:20:14 PM »

There is nothing stopping you from using a 6mm setscrew either (to supplant the o-ring trick).

db22 · « **Reply #12 on:** August 13, 2011, 01:22:33 PM »

Quote from: TwoTired on May 17, 2011, 11:28:16 AM

The shafts do not normally reach all the way into the chain tunnel. They are limited in their inward travel. If yours have worn through, the cylinder cover needs replacement.

Normally, the inward travel is limited, but the shafts are free to rotate, which can wear the cover shaft bore holes oblong. This ruins the geometry and screws up the cam lobes and followers. If the bore holes have not yet worn badly, the added orings help hold the shafts in place so the rocker pivots on the steel shaft rather than the shaft turning against the soft aluminum of the cover.
I know of no long term studies that prove this. Though I have added orings to shaft ends in hope that it will extend the cover life of a brand new one I installed ($255). It made the installation of the end plugs difficult, the result of squashing the orings between end plug and shaft.

Cheers,

Oh boy . . . Having read through the threads concerning this lovely situation, I went out to the garage and discovered that my 1975 CB550K suffers with this problem. The only ovalization I can see is in the intake (rear) side, on the left (over #1). The right side looks concentric. I suppose it's too late to try the o-ring trick, eh?

Should I stop riding the bike? I ride like a grandpa -- lots of miles at 50mph or less. I don't know when I'll be able to afford the parts and find time to install them. What's the best surce for a 1977 or later cam cover?

TwoTired · « **Reply #13 on:** August 13, 2011, 01:53:19 PM »

It's bad news. But, it takes quite a while to be terminal.

Eventually the cam and rocker go bad as well, because of uneven wear on those parts. I have reused some worn parts after fixing the cam cover, so far so good. Certainly the sooner it is addressed, the better, to a wear point. Then it doesn't matter, as the parts will have to be replaced anyway. Can't really tell from the outside.
It can all be fixed with the engine in the frame, though. With parts on hand, 2-3 hours work.

Cheers,

db22 · « **Reply #14 on:** August 15, 2011, 09:22:46 PM »

Quote from: TwoTired on August 13, 2011, 01:53:19 PM

It's bad news. But, it takes quite a while to be terminal.

Eventually the cam and rocker go bad as well, because of uneven wear on those parts. I have reused some worn parts after fixing the cam cover, so far so good. Certainly the sooner it is addressed, the better, to a wear point. Then it doesn't matter, as the parts will have to be replaced anyway. Can't really tell from the outside.
It can all be fixed with the engine in the frame, though. With parts on hand, 2-3 hours work.

Okay -- I found a late-1977 rocker cover, complete with rockers and shafts assembled, on eBay. The photo showed the rocker bearing surfaces to have shiny, even wear. 70 bucks -- does that sound reasonable? Seller says the shaft holes are still round. Should I trust the Clymer and Haynes manuals for procedures to remove the old one, install the replacemnt, and make the necessary adjustments? Does the big o-ring normally survive?

I have been riding my daily commute to work for some weeks now, and until I get the replacement installed, I will continue to ride the bike conservatively unless I hear the ticking sound getting louder. Getting 45 to 50 miles per gallon, and on the Relay I got 54.7mpg from one tank.

As always, my sincere gratitude goes to all the experienced hands on this forum who have made it possible for me to make this old bike run.

db22 · « **Reply #15 on:** April 05, 2012, 06:49:55 AM »

The used rocker cover installed with ease, and the ticking noise disappeared immediately. Still can't believe my luck that I found a complete cover and rocker assembly. Yet another '77 part on my '75 bike.

Kenzo1979 · « **Reply #16 on:** August 13, 2013, 05:58:14 AM »

I know this is an old thread, but it's about to be new to me this winter. I'm looking to do this upgrade and was hoping to get some exact instructions for this procedure. I read the Mike Nixon article, but it still leaves some questions.

Does anyone have detailed pics of this upgrade?

Are the O-rings that he suggests using, the ones depicted in #20 (lower left) on this parts fiche? (6mm x 3mm).

When he talks about the "two aluminum sealing washers under the camshaft end-cap hold-down brackets (http://www.motorcycleproject.com/motorcycle/text/500frockerbox3b.html," is that the washer on the bottom? And where do you get one of that exact size?

TwoTired · « **Reply #17 on:** August 13, 2013, 10:15:51 AM »

The o ring "fix" is really only viable if the cover shaft holes aren't already worn.

strynboen · « **Reply #18 on:** August 13, 2013, 10:23:46 AM »

off topic..but have somone a ekstra rpm gear..or a link...cms .nl does not have them..hope somone have a ekstra from a worn rocker shaft

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Author Topic: Cb500 Rocker Shaft Upgrade (Read 2343 times)