Topic: 1974 CB550 Ticking After Top End Rebuild + Cam Swap

[Mkubs]

Hi everyone,

I recently took apart my top end for a rebuild in addition to a CB650 cam swap. All seemed to have gone well as I did the following...

• Removed old gaskets
• Honed cylinders
• Put in new pistons with new piston rings
• Cleaned valves
• Lapped valves and valve seats
• Put in new gaskets/seals
• Swapped the 550 camshaft with the 650 camshaft (as mentioned above)
• Replaced rocker pins

After finally getting everything put back together, there was ticking. I think I found the primary reason for the ticking, which I believe ended up being an exhaust leak. I cranked the nuts down more than I thought would be needed and it helped. I am unsure if I should risk pushing my luck and crank them down further.
However, there is still a mechanical ticking. It primarily happens as I rev the bike and the rpms start dropping back down.

Things that I tried in a panic:

• Redoing my valve adjustement (total of 3 or 4 times)
• Double checked my timing on my Dyna S ignitiom (it was spot on)
• Synced carbs
• Double checked that the shaft was properly positioned at 1/4 TDC (picture included - it was correct)
• Readjusted cam chain tension

I lost sleep thinking that I adjusted the wrong cylinder when starting my valve adjustement. Normally, the cylinder with two loose rockers is the one to be adjusted (simplified, I know). However, after I put the new cam in, there were no more than 1 loose rocker on any given cylinder at TDC...I thought this would be due to the larger lobes. I truthfully didnt think twice about how to confirm which one is in the compression stroke and just started adjusting per the instructions. This morning, I did some more research and found that I can tell which one is in the compression stroke by watching the valve go down, then up, and then follow that to the next TDC mark. Turns out, I got lucky and adjusted the cylinders in the correct order.

I've attached two videos and some pictures for review. You may notice in the second video that there is quite a bit of smoke. I THINK this is the engine assembly lube I used throughout the cylinder head (lobes, bearing surfaces, rockers, NOT the cylinder walls) burning off. However, it hasn't really stopped burning off and I've had the bike running for maybe a total of 6 to 8 minutes. I would've thought it'd be burned off by now and now I'm concerned that there may be another cause.

I'm now unsure where to go from here...
Everything that I've check seems to be in good shape. At his point, the only thing I can think to check are my pistons/piston rings/cylinders. Maybe I missed something when putting that back together? Maybe one of the rings came loose?
Prior state of the bike was that it had a very very light ticking which I determined to be rocker valve wear, a known issue on this version of the rocker/valve cover. Besides that, not much else as far as problems go. It only has around 16k miles on it. 
I'm trying to avoid taking the whole top end apart again, but if that's where the suggestions point to, I'll jump right on it.

Thank you all again for the help - I greatly appreciate any feedback!
Mat

Bike info:
- 16k miles
- Rejetted for air pods
- Delkavic 4-1 exhaust

Edit: Video wouldn't fit. I uploaded a short on YouTube. The second half of the video shows the issue a bit better. Please use this link - https://youtube.com/shorts/-EvAZl5VPnU?si=XUl3zkaRTC3W528u

[bryanj]

I do know that fitting a 650 cam into a 500/550 can have clearance issues between cam lobes and casting

[BenelliSEI]

Have you pulled a valve cap? Is there lots of oil at both ends of the cam box?

Why so much blue smoke out the breather/filter?

[denward17]

Have you checked the rocker shafts inside the valve cover bores for looseness ?

[Mkubs]

I do know that fitting a 650 cam into a 500/550 can have clearance issues between cam lobes and casting

I did a quick check across all walls where they come close. Everything cleared, but by a tiny margin. I just read another comment mentioning that the heat inside the engine may cause the metal to expand enough to interfere. I will open the valve cover again and check.

Have you pulled a valve cap? Is there lots of oil at both ends of the cam box?

Why so much blue smoke out the breather/filter?

The amount of oil seemed to be a sufficient amount. Neither alarming low nor excessive. But I will re-check the end caps to see if anything changed.

Have you checked the rocker shafts inside the valve cover bores for looseness ?

That's a fantastic idea. I'll add that to the list of things to check.
I actually replaced them with long rocker shafts from what I believe to be an earlier CB500. I did check the parts diagram and the linger shaft was a replacement to the 8 individual short shafts (of which match the CB550 short shaft part number).

[denward17]

If an older valve cover was used, it may be too worn inside the shaft bores.

I had a major ticking in my '76 550 and the problem was the valve cover bores were worn, had to go to a pinned shaft type from a 77/78 valve cover.

[M 750K6]

You have a dilemma. If you idle the motor for too long without load on the engine, you risk not getting a good seal on the new rings in the bores. But the ticking may cause self destruct if you ride it.

I don't know the implications of a 650 cam in a 550. Have you checked the clearance in the cam's bearing surfaces? As Bryanj said, from the photo, the nearest cam lobe looks very close to the head casting. The tapping noise, difficult to tell on the audio from a video. It sounds like metallic contact. Have you confirmed it is definitely coming from within the head? Does sound like valve clearances too large. Does the different cam alter the required clearances? If it's higher lift, will it require stronger valve springs and could you be hearing the tappets bouncing back onto the lobe?

Have you checked whether there is any excessive movement of the new camshaft, including from side to side (end play)? Are the cams meeting the lobes nice and square, so they're not causing any lateral movement of the rockers? Don't recall the details, but there's a YouTube video from 'Superbike Surgery' on a similar ticking problem with a 1970s SOHC CB400 after a head refresh. Recorded 3 or 4 years ago, during Covid lockdown. He tracked it down to some wear creating end play, I think on a worn rocker? Worth a search and seeing how he found it.

Possibly slack cam chain, although it sounds more rhythmic than that? I don't know if the cam chain tensioner on a 550 is as finicky as the 750. The 750's tensioner piston can stick (mine was) and benefits from a clean and polish up. Also, the 750's cam chain tension needs to be set at a certain timing point on compression of no.1 (I think 15 degrees A or B TDC) don't know if 550s are similar?

[Mkubs]

If an older valve cover was used, it may be too worn inside the shaft bores.

I had a major ticking in my '76 550 and the problem was the valve cover bores were worn, had to go to a pinned shaft type from a 77/78 valve cover.

Only the rocker shafts from the 72 CB500 were used. But you definitely have me thinking about my valve cover. I'll check to see if the manual specifies specs of the bore and shaft diameters. Added to the list! I may even try putting the original shafts back in and do an A/B test.
Thank you for the feedback!

You have a dilemma. If you idle the motor for too long without load on the engine, you risk not getting a good seal on the new rings in the bores. But the ticking may cause self destruct if you ride it.

I don't know the implications of a 650 cam in a 550. Have you checked the clearance in the cam's bearing surfaces? As Bryanj said, from the photo, the nearest cam lobe looks very close to the head casting. The tapping noise, difficult to tell on the audio from a video. It sounds like metallic contact. Have you confirmed it is definitely coming from within the head? Does sound like valve clearances too large. Does the different cam alter the required clearances? If it's higher lift, will it require stronger valve springs and could you be hearing the tappets bouncing back onto the lobe?

Have you checked whether there is any excessive movement of the new camshaft, including from side to side (end play)? Are the cams meeting the lobes nice and square, so they're not causing any lateral movement of the rockers? Don't recall the details, but there's a YouTube video from 'Superbike Surgery' on a similar ticking problem with a 1970s SOHC CB400 after a head refresh. Recorded 3 or 4 years ago, during Covid lockdown. He tracked it down to some wear creating end play, I think on a worn rocker? Worth a search and seeing how he found it.

Possibly slack cam chain, although it sounds more rhythmic than that? I don't know if the cam chain tensioner on a 550 is as finicky as the 750. The 750's tensioner piston can stick (mine was) and benefits from a clean and polish up. Also, the 750's cam chain tension needs to be set at a certain timing point on compression of no.1 (I think 15 degrees A or B TDC) don't know if 550s are similar?

As far as the cam swap goes, from everything I've read, the only related modification is the tach gear to make it compatible with the camshaft. Besides that, it's essentially a drop in change. I haven't read that many folks need to take material off the housing, which is probably why I didn't think to consider it a heavy possibility. I took a look at the lobes after running it for the first time after hearing it tick and didn't see any damage to the lobes or housing. However, I'll give it a closer inspection tonight/tomorrow night.

I've tried checking for any play around the camshaft and notice no extra play. But I definitely find the idea of a worn rocker worth checking out again. The last time I checked, the rocker surfaces seem to be in good shape - all smooth, no pitting, no scratching, etc.

Also, as soon as I saw your note on the cam chain tensioner setting, I booked it to the garage because I definitely didn't do it the right way. After setting the engine to 15 degrees after TDC on cylinder #1, I did the cam chain adjustment. Unfortunately, no improvement. I was really hoping that was going to be the silver bullet to this issue. But at least I know have a properly adjusted cam chain.

[denward17]

If you take off the valve cover end caps, you should be able to screw a bolt into the end of the rocker shafts (I think  6mm?).

If you can, don't pull it, just wiggle up and down to see if you have movement.

When I checked mine, #1 intake side was loose.

Another thing I noticed is that my tappet measurement was no longer what I set it to just a couple of days before.

[denward17]

This is what mine sounded like:

https://photos.app.goo.gl/uctxPgNrLvYUMEsb7

[Mkubs]

If you take off the valve cover end caps, you should be able to screw a bolt into the end of the rocker shafts (I think  6mm?).

If you can, don't pull it, just wiggle up and down to see if you have movement.

When I checked mine, #1 intake side was loose.

Another thing I noticed is that my tappet measurement was no longer what I set it to just a couple of days before.

That is a great idea! I was going to make it way more complicated than it had to be. I'll check them out tonight. I'd imagine ANY movement that isn't rotational movement is bad.

This is what mine sounded like:

https://photos.app.goo.gl/uctxPgNrLvYUMEsb7

That sounds familiar 
I really appreciate the feedback and help. It's been added to the list!

[Ozzybud]

 (simplified, I know). However, after I put the new cam in, there were no more than 1 loose rocker on any given cylinder at TDC...

As you mentioned in your original post.

When removing and replacing the valve cover did you back off the tappets all the way? They should have all been loose
 If not you could have bent the valve stems when re installing the valve cover

[Mkubs]

(simplified, I know). However, after I put the new cam in, there were no more than 1 loose rocker on any given cylinder at TDC...

As you mentioned in your original post.

When removing and replacing the valve cover did you back off the tappets all the way? They should have all been loose
 If not you could have bent the valve stems when re installing the valve cover

Well that would stink. I did not have the tappets backed out all of the way.
At this point, that also seems likely. After checking the other items on the list, that will be the last thing I check. I'd imagine that would also damage the cylinder head if the valves stems are bent.

[Ozzybud]

(simplified, I know). However, after I put the new cam in, there were no more than 1 loose rocker on any given cylinder at TDC...

As you mentioned in your original post.

When removing and replacing the valve cover did you back off the tappets all the way? They should have all been loose
 If not you could have bent the valve stems when re installing the valve cover

Well that would stink. I did not have the tappets backed out all of the way.
At this point, that also seems likely. After checking the other items on the list, that will be the last thing I check. I'd imagine that would also damage the cylinder head if the valves stems are bent.

If some stems are bent they will stick down and cause all sorts of noise. If they are bent bad enough they can come into contact with the pistons and bend the stems on that end.

Don't run it anymore!


There are many threads on here discussing this topic and the proper. R & R procedures.

Here is one
http://forums.sohc4.net/index.php?topic=69622.0

[Mkubs]

If some stems are bent they will stick down and cause all sorts of noise. If they are bent bad enough they can come into contact with the pistons and bend the stems on that end.

Don't run it anymore!


There are many threads on here discussing this topic and the proper. R & R procedures.

Here is one
http://forums.sohc4.net/index.php?topic=69622.0

Oh, I should clarify that I did make sure that the tappets were not sitting incorrectly on top of the stems as I tightened the cover onto the cylinder head. I kept the tappets up as they were being lowered - but I definitely did not back them out all the way, which would've been a much better route.
Do you think this lowers my risk of having bent stems? I'd imagine the only thing that could have happened is the valves being pushed in a little further. Either way, I think for peace of mind, I'll end up checking my stems.

[scottly]

Oh, I should clarify that I did make sure that the tappets were not sitting incorrectly on top of the stems as I tightened the cover onto the cylinder head. I kept the tappets up as they were being lowered - but I definitely did not back them out all the way, which would've been a much better route.
Do you think this lowers my risk of having bent stems?

You should be OK.

[Ozzybud]

If some stems are bent they will stick down and cause all sorts of noise. If they are bent bad enough they can come into contact with the pistons and bend the stems on that end.

Don't run it anymore!


There are many threads on here discussing this topic and the proper. R & R procedures.

Here is one
http://forums.sohc4.net/index.php?topic=69622.0

Oh, I should clarify that I did make sure that the tappets were not sitting incorrectly on top of the stems as I tightened the cover onto the cylinder head. I kept the tappets up as they were being lowered - but I definitely did not back them out all the way, which would've been a much better route.
Do you think this lowers my risk of having bent stems? I'd imagine the only thing that could have happened is the valves being pushed in a little further. Either way, I think for peace of mind, I'll end up checking my stems.

That would lower the risk yes. The problem also being that the rocker needs to be tightened to go straight down. That is impossible since some of some of the lobes are on the high point and some on the low. We cant tighten all the screw simultaneously. hopefully you did not damage anything. The bonus being that you will never do this again!

[jonda500]

Oh, I should clarify that I did make sure that the tappets were not sitting incorrectly on top of the stems as I tightened the cover onto the cylinder head. I kept the tappets up as they were being lowered - but I definitely did not back them out all the way, which would've been a much better route.
Do you think this lowers my risk of having bent stems?

You should be OK.

+1 Should be fine. I used to do it that way back in the eighties when I was younger and dumber - sometimes the tappets wouldn't even need adjusting! The problem with it is the fragile threads in the aluminium cylinder head get worked real hard (or damaged) passing through slightly cocked holes whilst trying to pull down the cover and compress some of the valve springs at the same time.
John

[Mkubs]

Alright, I was able to check some items off of the list this morning.

• There was no substantial up/down play in the rocker shafts. Only one of the rocker shafts was able to be easily pulled out. I didnt pull fully, just wanted to see if it could be removed.
• I checked the side to side play of the camshaft and there was only 0.008in of play.
• There is absolutely no interference b/w the larger lobes and cylinder head....thank goodness.
• The diameter across most of the rocker shafts is between 11.95 to 11.96mm.
• The lobes and rocker surfaces look to be in really good shape, but I'm no professional so I'll let you guys be the judges.

The one item that I found to be peculiar was the side to side play of the rocker. My Clymers manual states no more than 0.004in-0.008in (.01-.02mm) of side to side play on the rockers, but after checking my rockers, the gap between the end face of the rocker and the cover wall was 0.032 (.8mm)!
I then took a look at a spare CB550 cover I had and the gap was 0.009in. I'm not sure why there is such a discrepancy since it doesn't look like material was removed from the cover. Any thoughts on this weird gap? Didn't seem to be much of an issue before the top end rebuild/cam swap.

As far as next steps, I'm thinking I put back the old rocker shafts, at least the ones that don't look worn, and see if there is a change to the ticking.

Looking forward to any feedback on these finds!
Also, here is a link to another short of the rocker play and camshaft rotation - https://youtube.com/shorts/nzRAd1u59K4?si=qS4I4ei_0rCUX-Lg

Edit: Getting pictures on here through my phone is much more challenging than I thought. I'll have pictures posted shortly.
Edit#2: Pictures added

[denward17]

If you take the valve adjustment caps off the valve cover, and look underneath them, do you see any witness marks?  (meaning is anything hitting the under side of the valve tappet caps).

[Mkubs]

If you take the valve adjustment caps off the valve cover, and look underneath them, do you see any witness marks?  (meaning is anything hitting the under side of the valve tappet caps).

There is only one cap that has some damage to it, but that was from before I owned the bike. I assume the PO made a mistake at some point and forgot to set one of the tappets to spec. Since I've had it, there have been no other issues or damage to the tappet caps.

[Mkubs]

I checked for any "ovaling" of the rocker shaft bores and could not identify anything by eye. However, I swapped some shafts around and could feel a minute amount of play. So I pulled the trigger on a pinned valve cover with shafts and am hoping that'll help with what sounds like valve lash.
A suggestion came through Reddit that the oil passages to my cam shaft may be blocked/clogged. I haven't confirmed this yet, but that might explain the lack of oil at the very ends of the camshaft and may also explain the smoke. I'll be checking those items tonight and will be sure to share my findings.

Thank you all again for the feedback thus far!

[RAFster122s]

Hopefully you are not mistaking the normal rocker & timing chain noise of these motors for a problem.

[Mkubs]

Hopefully you are not mistaking the normal rocker & timing chain noise of these motors for a problem.

Sure hope I'm not, but I'm fairly confident it's irregular. If you check out the YouTube short link in my first post and watch the second half of it, I think you'd agree. But let me know if you don't! I could just be crazy.

[Mkubs]

Howdy folks - it's been a while, but I've tried a few different things that I thought I'd list out here...

• Re-installed the exhaust/headers to ensure there is no exhaust leak
• Re-lapped the valve and valve seats
• Swapped cylinder heads with different valves because I thought it may have been my valves and valve guides

None of these got rid of the tapping sound. However, I did the classic screwdriver to the ear trick and pinpointed that a fair amount of the tapping was concentrated at the cylinders. Which made me think there may be something wrong with my pistons.
I looked into piston slapping, and now I think that's exactly what's happening. I checked my pistons a while back and noticed that they can pivot quite substantially about the wrist pin, but I didn't think anything of it because it seemed like the rings were still making solid contact. I attached pictures for feedback. I plan on taking the top end apart again (for the 4th time!!) to measure the bore, the pistons, and the rings.
Maybe I completely missed that my cylinders have been bored out? I don't know, but I'll definitely  be checking this weekend.
Let me know what you guys think!

Thanks!