Topic: Advice Needed: CB550 Exhaust Valves Snapping Shut

[754]

Looks like it should work..

[justinfinite]

Looks like it should work..

Ordered. I'll report back as you've suggested, in your prior post.

I'm certainly feeling much more confident with all of your expertise and advice, guys. Can't thank you all enough!
- Justin

[justinfinite]

Inspecting the head while I await the valve spring compressor. Is it standard for the exhaust valves to sit lower than the intake valves?

[scottly]

You might as well pull the head and see if the valves are stuck a bit open, but be sure to check the cam timing first, Before you remove the cam.

[gpzkat]

I just 'rent' (i.e. borrow for free) one from Auto Zone, it's not a very good one, it isn't a C clamp style, you use a wrench to compress. You have to take your time and keep an eye on it, and possibly bend the two tangs it in a bit to fit a bit better, though I would never do that...

[Tracksnblades1]

Can you watch the cam lobe, rocker, and and valve as you slowly turn the engine? As the exhaust lobe starts going down, does the exhaust valve stay open, then later snap shut?

When I had rocker cover installed, I was able to watch the exhaust valve slowly open, then stay open as the crank got hard to turn over at TDC. Then with a little more pressure, the exhaust valve snapped shut and the engine spins smoothly again, until the next rotation when the same situation would happen to the next exhaust valve in sequence.

To answer your question regarding the cam lobe, I was unable to visually see how the lobe was contacting rocker during rotation.  I am unsure if the lobe was or wasn't making contact with the rocker at TDC when the valve snaps back.

Paragraph 2,  Sentence 1, after 2nd comma. "as the crank got hard to turn over at TDC."

Why did it get hard to turn over...?
Sparkplugs in or out...?
Light Metallic hard to over or ?

Sounds like you found your problem on every revolution....

[justinfinite]

Update: I pulled the head and lifted the cylinder about 1/2 inch. Removed the cam chain tensioner and confirmed that it has damage. It appears that the retaining plate that held the adjuster bolt in place was a bit loose. So the bolt would ride high on the teeth and it wore the first two down. They wouldn't engage at times and they would other times.  This, combined with the tensioner possibly not being seated correctly.

I have a spare seized motor that I am going to try to open up and salvage the tensioner assembly.  I have not pulled a valve yet for straightness, but plan to do so.

Thanks,
- Justin

[calj737]

Update: Removed the cam chain tensioner and confirmed that it has damage. It appears that the retaining plate that held the adjuster bolt in place was a bit loose. So the bolt would ride high on the teeth and it wore the first two down. They wouldn't engage at times and they would other times.  This, combined with the tensioner possibly not being seated correctly.

How very odd. Who would have thought this could be a contributing factor?

I hope your spare has a good, usable tensioner!

[754]

Regardless of your cam chain or adjuster, if valves are sticking or hanging up they are bent.

[MRieck]

I guarantee they are bent. You'll see if the guides are cracked.....they usually do on the 550's

[justinfinite]

How very odd. Who would have thought this could be a contributing factor?

I hope your spare has a good, usable tensioner!

I agree.  Luckily, I was able to salvage the tensioner from the seized motor and it functions as should. Very thankful!

I guarantee they are bent. You'll see if the guides are cracked.....they usually do on the 550's

Regardless of your cam chain or adjuster, if valves are sticking or hanging up they are bent.

I agree with your assessments, and will need to pull the valves now that I've received the valve spring compressor that I ordered. I do plan on installing the head, as is, for my due diligence to ensure that the issue still persist with the working tensioner installed. I will report back with my findings. Thank you for your advice and recommendations. I'd certainly be at a loss without this community.

In the meantime, enjoy these photos of the motor that I opened to obtain the working tensioner. I wonder why it was seized!? 

[bryanj]

Thats secret additive SH1TE

[jonda500]

Regardless of your cam chain or adjuster, if valves are sticking or hanging up they are bent.

+1 fixing the tensioner can't possibly make any difference to the sticking valves
John

[Maraakate]

If you did not heed the warnings to hold up the rockets you have bent the valves and also possibly cracked the valve guides, if so cheapest fix is a second hand head(500 and550 are all the same ) and this time read the Honda manual CAREFYLLY before reassembling

I believe you, but where is the warning in the service manual for this?  I am looking in the book now as I may have this job coming to me soon.

[flatlander]

the warnings are all over this forum. the manual is not as explicit about it as some people here 
general advice is to hold them up with rubber bands. i find that too much faffing, and just pop them up with my fingers while putting the cover on. the point is to make sure that they sit loosely on the valve stems and don't bind.

[Maraakate]

the warnings are all over this forum. the manual is not as explicit about it as some people here 
general advice is to hold them up with rubber bands. i find that too much faffing, and just pop them up with my fingers while putting the cover on. the point is to make sure that they sit loosely on the valve stems and don't bind.

I have looked at that CB500/CB550 manual available here in the Engine section and I have not seen a single mention or warning.  Is it in some other manual?

[Scott S]

 It's in my factory service manual in the engine assembly section.

 For the rubber band trick, loop the rubber bands under the intake and exhaust rockers, going over the top of the valve cover, so that it holds them up. Once the valve cover is installed, just cut the rubber bands and remove them.

[Maraakate]

It's in my factory service manual in the engine assembly section.

 For the rubber band trick, loop the rubber bands under the intake and exhaust rockers, going over the top of the valve cover, so that it holds them up. Once the valve cover is installed, just cut the rubber bands and remove them.

I saw that in the manual, but that seemed more of a warning to just be sure that it is not going cockeyed on reassembly.  But OK, thanks for the clarification.

[bryanj]

It actualy says in the note to check

[Maraakate]

It actualy says in the note to check

It says to check that its properly meeting the valves.  But it's kind of an afterthought.  I always translated it to mean that the first time you're turning the crank (slowly) make sure that the lifters aren't binding and that the arm isn't cockeyed.

[bryanj]

Sorry to say you read it wrong

[754]

 This is the problem  with new bike people today, they dont use manuals like we did.
Some of them start working on the bike, then turn to internet when they get stuck .
 Some download a PDf and refer  to it when they desire... cuz they want to save 20 or 25 bux on a manual, or they want it NOW due to bad planning.. or whatever reason..

 AND THEN THIS HAPPENS....or something else screws up because you DONT have a MANUAL..

Let me tell you how a lot of us learned.  We bought a bike.. then we bought a Manual.  And then we would READ that Manual..ll.sometimes actually sit down and read or flip through .. find something interesting  and read up on it. And then believe  it it or not ..if we wanted to do Engine Work.. we would read up on it.. actually study it and get FAMILIAR with a procedure  BEFORE we started.... and then it usually went smoothly and well..
 
 But that does not happen much anymore.. people are in a RUSH.. the skim thru and MISS things.. and don't PREP for an upcoming work session..

 Like I have said before, the 20 to 40  dollar manual was the cheapest thing you could have bought for your bike..

[bryanj]

Hear, hear

[robvangulik]

+1, I still have manuals in my "library" referring to bikes that have been sold decades ago.

[Maraakate]

I bought a Clymer manual its on its way.  However, I have read the entire PDF front to back multiple times.  I just read them for anything I own in their entirety out of curiosity and I think its good that you should be familiar with any engine you intend to maintain.  With that said, it seems the older Honda manuals do assume things l which is why I ask many questions before I do stuff because you never know.  It doesn't hurt to ask and to get the reasons why.