Topic: How bad are worn rocker shafts?

[kurtkarram]

I have a 73 cb500 developing a tick on the #1 intake. Removing the cover shows that the shaft has egged out the hole a bit. I used a small o-ring to press between the cover shaft and the rocker shaft, which slightly helped the tick quiet down, but it's still there.

I am on the hunt for a 77-78 head with pinned shafted, but my question is how deadly does this symptom become for the rest of the engine? I am planning on doing a 50 mile trip to the beach in 2 weeks, I want to make sure my bike will make it there and back.

[Bankerdanny]

It makes it impossible to properly set valve clearance so you have valves that open too much or not enough, either being an issue.

Can you ride it on a 100 mile round trip, yes, you probably can, but I wouldn't put on too many miles without a replacement valve cover and wouldn't be pushing the engine very hard RPM wise.

[kurtkarram]

It makes it impossible to properly set valve clearance so you have valves that open too much or not enough, either being an issue.

Can you ride it on a 100 mile round trip, yes, you probably can, but I wouldn't put on too many miles without a replacement valve cover and wouldn't be pushing the engine very hard RPM wise.

What makes it not possible to set up valve clearance? I was able to set it fine. Is it something that would change the clearance when I rotate the engine and check the clearance again? Because I did not check that.

Also, what about the egging causes the ticking noise? is it the shaft itself slapping up and down in the hole?

[bryanj]

If the shaft can move so can the rocker arm on its pivot (the shaft) which alters the tappet gap

[dave500]

worst cases the tappet screw can hit the rocker cap cover.

[TwoTired]

The shafts are supported at each end by the cover shaft bores.  Those bores wear unevenly, allowing the rocker to Kant side to side. This makes the rocker cam follower and cam to advance wear where all the lobe pressure is now concentrated.  They run quite some time in this condition.  But, the longer it runs under this situation, the more wear occurs to both cam and cam follower, and this effects the ability for that cylinder to attain the same power as others. The increased wear usually means tappet clearance changes with the wear. I’ve not seen it, but it’s possible the larger gap can allow the tappet end to hammer the valve stem tip, making it mushroom, and damage the valve guide upon removal.  So instead of just replacing the cylinder cover and cam you risk replacing or refurbishing the head, too.

[DJBlackRabbit]

I just bought a 78 cover off ebay and saw a few other ones in the 100-200 range. Some rough looking ones for even less.

[kurtkarram]

I just bought a 78 cover off ebay and saw a few other ones in the 100-200 range. Some rough looking ones for even less.

I’ve been searching eBay for the past week, have only seen 1 78 cover… vapor honed and $250… all he other covers listed are not the pinned shaft ones, unless you’re seeing something I’m not?

[tourmax]

If you plan to ride it, keep in mind that wear isn't linear, it's exponential.

Meaning, once wear starts, it wears faster and faster the more you operate the machine.

Just something to consider if you feel like "pushing it".....

[DJBlackRabbit]

I just bought a 78 cover off ebay and saw a few other ones in the 100-200 range. Some rough looking ones for even less.

I’ve been searching eBay for the past week, have only seen 1 78 cover… vapor honed and $250… all he other covers listed are not the pinned shaft ones, unless you’re seeing something I’m not?

I’ll look again but I got mine about 2 weeks ago. They might have been snatched up


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[DJBlackRabbit]

Yup looked again and none are there anymore, dam!!!


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[BomberMann650]

Two Tired is correct it can damage the valve.

Disassembled a couple of heads that had this rocker problem. 
Valve did not pass through the guide smoothly.

[maxheadflow]

Two Tired is correct it can damage the valve.

Disassembled a couple of heads that had this rocker problem. 
Valve did not pass through the guide smoothly.

And the cam and rocker..

[kurtkarram]

Found a guy on facebook with an updated cover, bought and shipped should arrive monday. I've only had the bike for 80 miles, only about 10 miles from when the ticking really started to get loud. Was pretty intermittent before that, hopefully there isn't too much damage done when I open it up. The rockers on the new covers look very good. Suggestions on keeping the "new" ones vs reusing the "old" ones onto the new cover? I saw some conflicting opinions on that on another thread. I guess it depends on the condition of my used rockers and cam so I'll find that out in a few days when I go to swap.

Also, is there any way to check for valve damage with just the cover off? I don't really want to take the whole top end off at this time, but I can't think of any way to check tolerances or freeplay with those valve springs still on.

[dave500]

ive mixed n matched rockers n cams and covers on these engines for years,so long as the pieces your mating together aint obviously worn or damaged you can get away with murder inside them,ive put many many miles on them aswell,the valves wont have any damage to the seat faces within the head,they will be fine,once its up and running a compression check might settle your nerves?

[kurtkarram]

Heres an update: Got my valve cover today along with a JIS #3 bit to get the cover bolts off. It made life to easy... really should have gotten one sooner.
Anyway, when taking the old cover off I inspected the components in there. The rockers all had good looking wear. The cam looked good on all lobes except for the one furthest on the left. It had a couple of tiny "divits" or "cavities" in it. Picture should be attached. I put it back together with the new valve cover and readjusted the valves. Bike ran much quieter with no ticking. I only let it idle for a few minutes with a couple revs. I'm assuming the carbs to be pretty out of sync now, so I will sync them tomorrow. Just a few questions.

Because they are new rockers onto the cam, will I have to readjust the valves soon after they "marr" to each other? (I think this is the term)

This cam lobe... was it a mistake to leave it in the engine?

[bryanj]

Ive seen worse last years, there is no big lip so should be ok.
Used followers and cam dont take long to bed in but good idea to do a service at 500 miles then 1500 miles

[kurtkarram]

Another update. I synced the carbs today, idles a bit better I guess. The real issue is another ticking has developed and I'm not sure why. After the first start it sounded perfect, but a ticking noise appeared after warming up, that is now present even 10 seconds after a cold start. I have attached a video. Using a screwdriver to my ear, It sounds like the exhaust tappet on #1 is making the noise. Not sure what this could be because the valve clearance is set properly. I had only ridden it about 10 miles since I installed the new cover and set the clearance, but I guess I'll check it again tomorrow. Maybe it's an exhaust leak? But i'm not sure what that would sound like.

On another note I have a vague memory of someone saying in another thread that oil should be shooting out of the tappet cover exhaust side if I take it off? I took mine off while running because I was curious, and no oil shooting out. I did see oil inside though, I'm not sure how much of a flow this should be.

sorry for turning this into another "ticking cb500" thread

Warm idle after carb sync and new valve cover:
https://youtube.com/shorts/lIKrovUgWb0

[BomberMann650]

Exhaust leak can make a ticking sound.

[dave500]

phone video always seems to make it sound worse,in the day these were a modern quiet motor compared to the old british twins etc,by todays standards they sound rattley,i wouldnt worry about it just recheck the valves and cam chain after a short while?