Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Neilw on August 03, 2026, 06:49:40 PM
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I've been rebuilding the Top end on my CB550, and it's not been without its challenges, but I have the rocker cover on now and am now attempting to set the valve clearances.
Quick back story - I had the top end bored out and new pistons and rings - which all went back together again quite nicely. The cam chain was another story, but I got there in the end. I had previous revoved all the valves, lapped them and reinstalled, including new seals.
When i installed the rocker cover, I loosened all of the valves to make it easier to get on; now I'm at the point of trying to find TDC. The video i'm following is pretty straightforward, but assumes you already have clearances that work, so you can identify whether 1 or 4 is on its compression stroke, so that you know you have the cam in the right position - hope i explained that correctly. Anyway, an alternative method was to put your thumb over the park plug hole of no 4, so you could feel the compression. This is where I'm having trouble - in fact I have two areas of concern
When I turn the engine over using a spanner, I get a loud snap back from one of the valve springs - could this be because of the slackened clearances? I can get it to happen on other valves by screwing in/out the adjuster. OR is there something more sinsiter going on?
How do I approach doing the valve clearences - is there something i can do to "reset" the clearences so i can work out if 1 or 4 is on the compression stroke?
Also, and i don't have a good feeling on this one - when i put my thumb over the spark plug hole for No.4, i got no compression or feeling of pressure, but i did when i repeated the process on No 1.
I guess i need to sort out the value clearences so i can see if that sorts out the snap back noise and also allow me to put a kick starter on, so i can test the compression properly.
It's quite possible i haven't installed somthing correctly, I'm new to this, but have been very careful as i've put the head together.
Any help or advice is greatly received - I'm just at a loss of how to proceed and need to clear thinkers to help me :-)
Many thanks in anticpation.
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A loud snap is worrying as it usually means a bent valve that is sticking in the valve.
Loosening all the clearances is simply NOT ENOUGH when refitting the cam cover, you have to hold all the adjuster ends up(rubber band trick) to make sure the followers are on the lobes so that the adjuster end can not get jammed on thetop of the valve stem and push against it bending the stem.
To set clearances you have to have the T 1-4 mark lined up with the static mark, at this point the lobes of the cam on either 1 or 4 will be pointing down, this is the one on compression, after setting turn crank CLOCKWISE 360 degrees and set the other cylinder, same for 2 and 3.
I hope you have not bent a valve but it does sound like it
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Refitting the 500/550 rocker cover needs some care
Ideally 4 rubber bands holding each cylinder rockers up from the valves
This is to stop the tappets bending the valve stems
When setting the clearance, 1-4 should be at tdc,just set the cylinder with the closed valves, then rotate one 360 degrees
2-3 are 180 from 1-4
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A loud snap is worrying as it usually means a bent valve that is sticking in the valve.
Loosening all the clearances is simply NOT ENOUGH when refitting the cam cover, you have to hold all the adjuster ends up(rubber band trick) to make sure the followers are on the lobes so that the adjuster end can not get jammed on thetop of the valve stem and push against it bending the stem.
To set clearances you have to have the T 1-4 mark lined up with the static mark, at this point the lobes of the cam on either 1 or 4 will be pointing down, this is the one on compression, after setting turn crank CLOCKWISE 360 degrees and set the other cylinder, same for 2 and 3.
I hope you have not bent a valve but it does sound like it
Oh S**t, that doesn't sound good.
So next step is to remove the head and check the valves, then go from there. If the valves are bent, could there be any other damage I shoud look out for?
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Do you have this or similar?
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Have a look in Ash's Dropbox at top of page as well.
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Do you have this or similar?
I do.
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A loud snap is worrying as it usually means a bent valve that is sticking in the valve.
Loosening all the clearances is simply NOT ENOUGH when refitting the cam cover, you have to hold all the adjuster ends up(rubber band trick) to make sure the followers are on the lobes so that the adjuster end can not get jammed on thetop of the valve stem and push against it bending the stem.
To set clearances you have to have the T 1-4 mark lined up with the static mark, at this point the lobes of the cam on either 1 or 4 will be pointing down, this is the one on compression, after setting turn crank CLOCKWISE 360 degrees and set the other cylinder, same for 2 and 3.
I hope you have not bent a valve but it does sound like it
Oh S**t, that doesn't sound good.
So next step is to remove the head and check the valves, then go from there. If the valves are bent, could there be any other damage I shoud look out for?
If you have bent a valve ,and turned the engine over you might have broken a guide
Best wishes
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Yes i hate to say it but to be certain remove the head(again), remove all the springs and check the valves slide easily through the guides, you should be able to see if a stem is bent, if not you are lucky , if one is check the valve guide carefully.
Should you end up in trouble all 500 and 550 heads are the same
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Yes i hate to say it but to be certain remove the head(again), remove all the springs and check the valves slide easily through the guides, you should be able to see if a stem is bent, if not you are lucky , if one is check the valve guide carefully.
Should you end up in trouble all 500 and 550 heads are the same
Thank you, I'll report back, may take a day or three :-)
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Thats ok, i am at work for 4nights from tuesday!, my email is in my profile if you want to contact direct, i also have a garagefull of "bits"
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Not being critical here Neil but sometimes I wonder how people do these things. You need cylinder 4 on TDC to fit the cam, you know it's there, you've been looking at it for ages. Why turn the engine? It's setup for installing the camcover, which incidentally I've never ever wound the tappet adjusters out, never used the elastic band trick either. I just hold them up with my fingers whilst looking at where the adjusters are settling as the cover goes down, a small turn on each bolt to ensure it goes down evenly. Never had a problem.
You had the valves out? I'm wondering if one of pot 4s valve springs have shed the collets.
Where in the UK are you? sure to be someone experienced near you who is willing to help out.
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Not being critical here Neil but sometimes I wonder how people do these things. You need cylinder 4 on TDC to fit the cam, you know it's there, you've been looking at it for ages. Why turn the engine? It's setup for installing the camcover, which incidentally I've never ever wound the tappet adjusters out, never used the elastic band trick either. I just hold them up with my fingers whilst looking at where the adjusters are settling as the cover goes down, a small turn on each bolt to ensure it goes down evenly. Never had a problem.
You had the valves out? I'm wondering if one of pot 4s valve springs have shed the collets.
Where in the UK are you? sure to be someone experienced near you who is willing to help out.
I'm learning as I go, so happy for my mistakes to be pointed out. As they say, every day is a learning day.
I can see the collets, so they are good. The Haynes manual didn't have much of a process for installing the rocker cover, so it looks like that may be the culprit. I was careful though and seated it the best i could before tightening the bolts down, a bit at a time. I didn't have any resistance, so no reason to doubt there could be an issue waiting round the corner.
You can bet your life that I won't be taking 6hrs again to fit the camshaft and chain when i get to that point.!
I'm based in Tonbridge, Kent.
I'll know more when i inspect the valves and head,
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Thats ok, i am at work for 4nights from tuesday!, my email is in my profile if you want to contact direct, i also have a garagefull of "bits"
Thank you, Bryan, i may well be scavenging for parts, hopefully not too many.
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Having worked on Hondas for more years than i care to admit I, like Ken, use only fingers but mention the rubber bands as its a known trick and helps the novice, we all had to learn
Go to Ashs dropbox at the top line and download the original Honda Manual, you will find a small pic in there of what we are talking about.
Glad to help however i can
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Shame you’re in Kent Neil, miles away from me near Manchester. I’d have been happy to pop over and fix the problem for you.
One thing I think I should mention, just in case. I remember you having a problem getting the cam chain onto the sprocket. Unless it’s a new chain you can normally do that with fingers only. A new chain tends to need a little help with some leverage. The reason you had a problem is almost certainly because you didn’t get the tensioner blade to retract enough. That puts pressure on the chain and causes you to suffer because it’s under tension already. The other mistake is people try and fit the tensioner after they have lowered the barrels, then you find getting the adjuster bolt through its hole in the barrels whilst also making sure the bottom part is engaged in its retainer slot in the lower crankcase means one of 2 things happen. You bend the tensioner at its lower end or you miss the retaining slot altogether. You don’t spot that unless you know it’s likely to happen and you’re so relieved it’s finally fitted you don’t think to check. That now means the tensioner is rubbing against the primary chain, lots of little pieces of metal slowly being ground off and going into the oil. Not good.
The foolproof way of avoiding both problems is to stop lowering the barrels around 2” above the gasket. Then fit the tensioner, it will now fit straight very easily. Get the blade and push it back hard after releasing the locknut. As soon as it bottoms tighten the locknut. Easy once you know how. Don’t fit the upper bolt until you’ve fitted the sprocket and then release the locknut. Leave it loose and then try and align the top bolt hole. Sometimes it refuses to line up and you need the tensioner loose in order to get it to line up. If you need to get the tensioner blade to fully retract whilst the heads still on, just release the locknut, slacken off the top bolt a little and use a big flat bladed screwdriver and lever it back, then lock it off.
If you’re worried you’ve missed the retainer slot in the lower crankcase you can check by removing the sump and looking up, you can see if it’s missed or not.
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So the jury is in, and it's not good news.
All of the valves are bent. I had to straighten them slightly to get them out by applying horizontal pressure at the top of each one.
What are my options now? I don't know the condition of the valve guides, and I don't know how to check.
Feeling gutted tbh.
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Easiest is a used head complete with valves, also cheapest way to get a full set of valves, as to guidessee if any have broken tops
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Easiest is a used head complete with valves, also cheapest way to get a full set of valves, as to guidessee if any have broken tops
Theres this one on Ebay? https://www.ebay.co.uk/itm/257610142722?_skw=cb500+550+cyclinder+head&itmmeta=01KZ68WP5D8CHZCAXHY5M53BY9&hash=item3bfac2d402:g:hOsAAeSw~klqTKGy&itmprp=enc%3AAQALAAABAGfYFPkwiKCW4ZNSs2u11xBs7J5UtyIjAPmqD9%2BgdFSqt%2B2zA%2FruhpU1522RFoFTen5%2FPPInSnLhTEC980dIuEnLY%2BT%2FFvnvWT9mvdF0R1N1e1HmmZ%2BPXIIBdQ3d9EztOWqStND3oe3sbvXSLIrqwjwx2mz8a507G6tI3ScRvuuT1j307Mcc7%2FYCpZs95kgfrHoUSzRlZXubCNRdhvRfaUGmV6Q5wEs%2F8tBMp4zE6go0jTNztdaqI63v2nv116DtL%2B%2BlIL39ASigIZLmqFQXXgln0Bsu0kjiCzZLJEAlimC8AGvsKFwW%2BaEuVLLRVVoLVFrBSb3ASCHEm5zt2eCUI6I%3D%7Ctkp%3ABk9SR-Tj8sj5Zw (https://www.ebay.co.uk/itm/257610142722?_skw=cb500+550+cyclinder+head&itmmeta=01KZ68WP5D8CHZCAXHY5M53BY9&hash=item3bfac2d402:g:hOsAAeSw~klqTKGy&itmprp=enc%3AAQALAAABAGfYFPkwiKCW4ZNSs2u11xBs7J5UtyIjAPmqD9%2BgdFSqt%2B2zA%2FruhpU1522RFoFTen5%2FPPInSnLhTEC980dIuEnLY%2BT%2FFvnvWT9mvdF0R1N1e1HmmZ%2BPXIIBdQ3d9EztOWqStND3oe3sbvXSLIrqwjwx2mz8a507G6tI3ScRvuuT1j307Mcc7%2FYCpZs95kgfrHoUSzRlZXubCNRdhvRfaUGmV6Q5wEs%2F8tBMp4zE6go0jTNztdaqI63v2nv116DtL%2B%2BlIL39ASigIZLmqFQXXgln0Bsu0kjiCzZLJEAlimC8AGvsKFwW%2BaEuVLLRVVoLVFrBSb3ASCHEm5zt2eCUI6I%3D%7Ctkp%3ABk9SR-Tj8sj5Zw)
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Dirty and will need dismantling to clean it all out but journals look ok. Your decision but I’d check your existing head first for guide damage. Someone on here is bound to have some spare valves, I had hundreds of them at one time.
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Dirty and will need dismantling to clean it all out but journals look ok. Your decision but I’d check your existing head first for guide damage. Someone on here is bound to have some spare valves, I had hundreds of them at one time.
Ok, so each of the valve guides is cracked at the top, which means replacement - and that is not a diy job from what i can see. So it's either a replacement head with guides and valves that are hopefully ok, or find someone to rebuild the head. :-(
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Yeah that’s toast. Skilled job to replace the guides, you need to recut the seats after as well. Much cheaper to find another head.
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Yeah that’s toast. Skilled job to replace the guides, you need to recut the seats after as well. Much cheaper to find another head.
Yep, pretty much what I thought - I'm looking for a head atm, and also emailed a company that does rebuilds to see what they would charge. Will decide in the next day or two.
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A rough guide to parts prices. A guide is approx £33 each and a valve around £17. Times 8 and it gets expensive real quick.
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Just thinking out loud!
Neil has done what I would have done and had a go so fairplay to him for doing this. Mistakes will be made and I have made a few in my time but that's how we learn if that is our inclination.
It's easy to "do up" a vintage bike with your cheque book but that's not why forums like this exist. I wish I could offer more in the way of knowledge but I am "a Neil" and willing to have a go and learn. It obviously helps if one has a competent local friend but for many of us the guidance offered by this forum is all we can hope for and I appreciate very much the kind and thoughtful people who are happy to pass on their knowledge in such an altruistic way.
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TBH Otis the damage caused means it wasn’t the way the camcover was fitted. As an ex Honda mechanic I’ve seen more than my fair share of “I have no idea how that happened “ mistakes. It’s not the first time it’s happened and it’s certain to happen again. As you say it’s how we learn. It’s such a shame it’s happened and it’s going to cost a bit to correct.
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TBH Otis the damage caused means it wasn’t the way the camcover was fitted. As an ex Honnda mechanic I’ve seen more than my fair share of “I have no idea how that happened “ mistakes. It’s not the first time it’s happened and it’s certain to happen again. As you say it’s how we learn. It’s such a shame it’s happened and it’s going to cost a bit to correct.
But you do not gloat and that makes you special. Enthusiasts come from all walks of life and if I had the knowledge and where with all I would help everyone. In this instance it will cost a bit to fix but what a lesson to have learned. At some time in the future Neil's experience will help another newcomer and that is how the cycle continues.
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I never gloat. The object is to teach others. Hence some of my lengthy posts. In time I’ll pass on and all my experience and knowledge will be lost. I feel it’s my obligation to pass on as much of that as humanly possible. I’ve known mechanics who refused to divulge secrets, they hoarded information like it was money. Or worse they’d mislead you, which is inexcusable.
A lot of the tricks commonly quoted on this forum originally came from me, I had a habit of thinking outside the box and coming up with novel solutions. If I didn’t tell anyone else they’d be lost when I pass on. That helps no one.
I have a cb1300 and on that forum I constantly pass on what I’ve learned, I even offer a shim swap service. I feel it’s the least I can do. I was very lucky to work in the trade, the amount of bikes I got to ride was unbelievable. A turbo charged GS1000 was a good one, popping a wheelie at 100mph was interesting.
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I agree with Ken and pass on what i was told by Honda travelling techs back in the day
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I think this forum and members are a community and also very helpful
Advise is freely given, as is assistance
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To echo whats been said above, such a shame to get this result from all the hard work leading up to it.
I think we all feel your pain on this one Neilw.
It is an odd one this, if you don't know about it. For those that are unaware, the rockers are best pulled up through the tappet cover holes and linked across the outside of the cover with elastic bands to hold them there while the cover is assembled onto the head. It has the effect of the rocker pads touching the cam lobes first, and not letting the rocker tips "snag" on the valve stems while tightening tbe cover to secure it.
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Thank you for all your support. I now realise the mistake I made, and it's borne from my lack of experience.
I didn't know that the rocker cover should have sat flat on the cylinder head. This wasn't explicitly stated anywhere, so when I fitted the cover and it sat about half an inch above the head, I thought that I should just tighten the bolts uniformly down until they met. Which is why I managed to bend all 8.
I guess, if I had been more thorough looking through the manuals, I may have spotted the bit about holding the rockers up. Note - none of the videos I watched on YouTube explained this!
So definitely a lesson learned.
Now onto sourcing a replacement head.
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I’m not of that opinion Neil. To bend all 8 I think you got the cam timing wrong. Maybe you finally got the chain on the sprocket and then moved the cam to align the bolt holes. Just a theory but would explain the results better than just snagging the adjusters on the top of the valve stem, 2 or 3 , yeah I’d say possible but all 8, mmm not sure. I think as you rotated the engine afterwards that’s what caused the valves to hit the pistons and explains the noise you could hear as well.
Either way, damned bad luck and I’m genuinely sorry you learned that lesson the hard way. If you hadn’t broken the guides I may have had 8 spare valves somewhere. I know I’ve got over 50 good cam followers in a box of oil, I even threw around 20 away. Never thought I could get them repaired with hard chroming. Live and learn eh.
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This is the trick to hold the rockers in place when you fit the top, one rubber band does a pair of opposing rockers, the adjustment screws were undone as much as possible.
I learnt this from NJ's rebuild
(https://live.staticflickr.com/65535/54086525790_3fff8f7e3e_b.jpg) (https://flic.kr/p/2qprzLJ)WP_20181111_16_44_15_Pro (2) (https://flic.kr/p/2qprzLJ) by Macabe Thiele (https://www.flickr.com/photos/187487200@N03/), on Flickr
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So an Update with some good and bad news!
BryanJ came to my rescue and supplied me with a replacement cylinder head with intact valve guides and a good set of valves. I've spent many days preparing, cleaning, painting and finally honing the valves, and everything seems good. Installing the springs with new valve seals went smoothly, and today was the day to fit the head and move forward.
I've had the head on and off twice, as I discovered that the front flange holes were blocked with some form of calcification, which I cleared with a reamer; all good and refitted.
I've torqued all the head bolts down, and I have now discovered that the flange bolts should have been torqued less (thanks, Haynes manual, for not mentioning that). As a result, I over-tightened the front flange bolt and stripped the thread in the lower cylinder head. It's not entirely gone; I can get it finger-tight, but no tighter.
So, now what are my options? Is there a diy fix? will it do as it is, as all other bolts are torqued correctly? I'm not quite sure how to proceed and whether i'm able to do it myself. The lower cylinder has been bored out, and i have new oversized pistons fitted, so i don't want to replace it.
I could cry!
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Helicoil will sort that
No hassle, just extra work
Those small bolts are prone to stripping
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Yup 6mm helicoil kil, not too expensive and you will use it more
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Phew, another new skill to acquire!
Anything to watch out for when buying a kit - i see cheap ones on ebay are they any good?
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Buy cheap and repent at your leisure! Things are normally cheap on eBay for good reason, 90% are absolutely crap! I bought a 90deg screwdriver to adjust the carbs on the NC30. A Seeley screwdriver was £40! I bought one on eBay for £12 and it lasted all of five minutes. It was so cheaply made inside the cable stripped as soon as I tried to adjust the balance screw that has a spring behind it, it is now in the bin and I've bought a decent Seeley item that I should done in the first place.
A good helicoil kit is made by a company called 'UniThead'. They should have a website. You get the full kit in a plastic box, worth the money and always works first time.
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With tools i would agree but i bought one of these about 3 years ago and so far bought over 100 coils extra, there is a nice tap holder i got as well if i can find that i will post it seperate
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The wrench i bought isnt for sale at moment but this is similar, means you dont need room for a standard tap wrench
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Just a quick update - and i've had a good day!
I purchased a Helicoil kit and thought I might be able to drill the holes while the cylinder head was in the frame. I decided against it due to access restrictions, but also so I could do a proper job.
I did front and back flanges to ensure no ongoing issues and, if i say so myself, did a good job, so one happy bunny.
Fitting the main cylinder head was straightforward and then the new head. All torqued down correctly, including the two flange bolts into their new Helicoil homes.
Fitting the chamshaft/chain was fiddly, but nothing like the whole day it took me last time, maybe an hour of messing around. Also made sure that 1 & 4 were at TDC and the slot was located correctly, which will save me time when i get to setting the tappets.
So i'm now back to where i was 4 weeks ago before i screwed things up.
I'll tackle fitting the rocker cover tomorrow afternoon.
Thanks for all the advice to get me this far. ALso have a set of Elastic bands care of my postman, ready to use. Fingers crossed.
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Most of us have experienced Groundhog days at one time or another, well done with your pereverance.
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Good for you
Can I suggest you completely remove the tappet screws and lock nuts,
Lol
Obviously the nuts stay on the tappets!
Get a card,8 holes
E1 to 4
I1 to4
Keep them in the same position
Keep up the good work
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Well done, only a couple of hints
1 make sure cam is right way round so the tacho drive works, i am NOT admitting to why that one
2 some jointing compound under the pontefract cakes or pucks as our us cousins call them!
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Well done, only a couple of hints
1 make sure cam is right way round so the tacho drive works, i am NOT admitting to why that one
2 some jointing compound under the pontefract cakes or pucks as our us cousins call them!
Thanks for the tip, I've ordered some jointing compound, so a days delay. I can continue work on the back wheel in the meantime. I had to double-check the cam shaft!