Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: bigmockuk on July 27, 2025, 12:55:38 PM
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ive had to take the head of my 550 k3 3 times to find out what the loud tapping sound was,it sounded like a very loose tappet even tho i knew they were all set,bike was misfiring on no 2 so while i had the head off i removed the valve springs thinking one had broken but all was good,so after i took out the camchain tensioner i saw what the issue was,about an inch n a half up from the bottom (facing towards back of engine) something has been hitting against it,so i thought maybe it had came out of place since i had did about 100 miles since barrel was last off,so i put it all back together and noise was still there >:( so pulled it apart again and put a slight bend where the shiny groove was from whatever could be hitting it,built it up and hoped it would be ok but its not,its not as loud but still there,any one any ideas as to what could be hitting against the bottom of the tensioner?
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Is the bottom end of the tensioner sitting properly in its groove in the case?
Very easy to fit it without it sitting in the correct place.
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Do you have any photos of the tensioner?
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The bottom of the tensioner sits in a pocket in the crankcase. Best to remove the sump and check that it is correctly inserted.
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i dont have pics which is totally unlike me i take pics of everything i work on,my next question has just been answered,can the tensioner be seen from below when sump pan is removed? so thats my next job,if its half dry tomorrow i`ll get the pan off,take some pics n hopefully find a solution,so i`ll upload pics of what i find,cheers guys
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steve W,the book says it just drops in,aye right! i had to fiddle with it before i could get it to sit properly and when the barrel was right down it wobbled like it was`nt sitting flush so took a few attempts to get it right,but i should see fom below if it is actually correct,cheers
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This is what happens if the bottom of the tensioner is not seated in its location.
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From memory, I think the Haynes manual says drop it in with the barrels. When the barrels are 10mm or so from being fully down, guide the end of the blade into its slot.
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This is the tensioner in the correct position. You can see a mark on the outside of the tensioner pocket where the bottom of the tensioner was before I stripped the engine.
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jonny4428 that pic you have of the marks on the tensioner is identical to the marks on mine!! which means its still not in place :-[ cheers for the other pic it lets me see what to look for when i drop the pan,ive seen two vids on youtube now that shows the tensioner being fitted to the barrels prior to lowering the barrel? might be a good idea to do this,could take away the guess work
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This is the end of the tensioner I took out of my engine which had not been fitted into the pocket by the PO.
The wear is from it being worn down by rubbing against the side of the primary chain, could that be the noise you are hearing. It’s on a K1 so could be a bit different to yours.
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Also I don’t feel that it’s possible for the tensioner to properly tension the cam chain when the bottom end is not supported in the boot. There must be a degree of flexing which would allow chain slap. This is often most noticeable on tickover and on the overrun, this could be mistaken for tapit noise.
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ye definately murf,that pic posted by johnny is exactly the same as mine so its hitting that chain,i hope to take it apart again either today or tomorrow so i`ll post my findings cheers
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got engine top half stripped down today and can verify that tensioner is i the wrong place,i also noticed a bolt had worked loose by quite a bit so eith vibration or PO not nipping it up
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having to upload 1 pic at a time as it wont allow 2 or more ?
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just to finish putting things back together tomorrow and give it a try now that tensioner is in place,Cheers guys for your help and assistance!
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Good photos thanks, hope it all goes well and everything is quiet when you run it up.
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Cheers Murf appreciate it,i`ll check in later todady :D
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Hi Guys looks like its back to the drawing board :'( started the bike up and tapping noise is still there even tho tensioner is in pace,gave it a few revs and noise didnt sound too bad so went for a run but 5 mins later the noise became a concern,loud tapping sound which rises with the revs and you would put your last buck on it being overly loose tappet,but is definately coming from the top end left hand side,right hand side has no sound at all its running quite,this sound is from the top left so thinking its either damaged valve springs on no1 cylinder or damaged rocker arm shafts,ive already had no2 valves out to check them and lapped the valves in too
,now wish i had did no1 also.i`ll take rocker cover off tomorrow and take shafts out to inspect things,if all looks good its head off time again to check no1 valves,strangely enough when i first got the bike i had to replace no1 valve and guide as there was a whole lot of side play in the inlet valve but all the rest were sound,weird,what could possibly have worn the valve away to such extent it wore away the guide! any ideas im all ears lol
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Got to ask, are you sure the exhaust gasket isnt leaking, many have chased noisey tappets only to find nipping up the flange cures it
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ye Bryanj just fitted new ones the other day too,just seen on DS that the tensioner is supposed to have a rubber dampener fitted at the end,mine doesnt so could it even be that resonating upwards
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Supposed to have one each end in the steel bit, usualy dont fall out
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so Bryanj you think maybe whenever the tensioner is removed the rubber may stay put? i`ll upload a small video to youtube at some point later today of a recording i took of the noise and post a link here if anyone can determine what it could be,this has only occured recently,the engine has been sound up to now so im asking myself was it something i disturbed? in which case its only been the tensioner .i hope to take the rocker cover off later and remove the shafts to check things are ok there and if not i`ll go further down to possibly fit new dampener rubber,im too stubborn to let this get the better of me but its chipping away at me haha.back to work shortly too then time will be against me.
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If the damper rubber is missing you need to replace it (them) otherwise the tensioner blade will be moving around and will have insufficient tension being applied to it.
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As said they don't come out until you remove the blade and I think they are hidden in the pockets at the ends of the blade.
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was so sure i`d find somethingoutof place upthe top end like a damaged rocker shaft or valve spring but found nothing,so this noise must be resonating upwards from down below and the only thing i can think of is the tensioner rubber at the bottom,as the camchain is moving round the tight spot that a chain has must be pushing the tensioner against the groove it located in and resulting in the tapping sound so thats the next job,hopefully get that done before the weather changes in the next few days :)
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I have been following your thread with interest. It occured to me earlier today and I remembered watching a video some time ago where a 400 four rebuild was giving similar noises.
In that instance the guy had used a reground cam and the old followers. Because of the mismatch in wear the rocket arm was slapping sideways on first contact and sounding like a loose tappet. I think a slowed down video confirmed it.
I guess the same could happen if the rockers end up in a different position after a rebuild.
It's on you tube somewhere.
Edit. Found it about 14 minutes in
https://youtu.be/k3qBLW_sYD8?si=LLzgM481N7aTsw_j
Regards
Dave
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That was superbike surgery. Twas a 400 four.
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Just a thought, it’s not the primary chain that is worn and slapping is it, you can see cut marks on the oil gallery cast in the crankcase if the chain is slack. (Sump plate off looking up)
Is the pad on the tensioner in good condition.
Is the cam chain guide in position and ok.
Do you slacken off all the tappet adjusters and back the screws out before fitting the rocker box back to the head, then reset them all.
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550 primary does not hit casing as much as 500
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Would it be fair to say the 500/550 camchain adjuster is the weak point in terms of design on these engines? When I rebuilt my engine i now wish I'd replaced the whole assembly, the slot in the adjuster screw is a bit chewed up making it hard to hold still while tightening the 10mm nut.
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Not really, its fine till its abused by somebody trying to remove any slack by turning the screwdriver slot.
If used solely as the manual says there are no problems.
The 500 primary chain does eat into the main oil gallery in lower crankcase but the 550 was a slightly different casting.
The most common fault on 500 was centre selector wear and on the 550 one gear can shear the dogs off but cant remember which
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Not really, its fine till its abused by somebody trying to remove any slack by turning the screwdriver slot.
If used solely as the manual says there are no problems.
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IMO, it's by far the shittiest part on the CB500/550s. What Bryanj doesn't tell, is that the mechanics at Honda dealers in Europe have been instructed by their resp importers on how to perform the adjustment best. That differed from what a customer reads in the manual. As it is sooo easy to damage the camchain tensioner assembly - it was designed far too fragile - Honda had done better not to give any instructions in the Owner's Manual on this, but to advise owners to have it done by a dealer.
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Whatever method you use Bryan's method. your Euro method or the manual, as long as you don't wreck the screw head the worst you get is maybe a slightly looser cam chain, not the end of the world.
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hi guys,im not long finished building the engine back up,decided to strip it back down and fit rubbers to camchain tensioner,but no joy! rattle is still there,the camchain guide is fine and i dont believe the chain is worn,after fitting chain to the sprocket and sprocket to camshaft i loosen adjuster nut when no1 cylinder is on commpression stroke and advance spring is in alignment with timing notch then the tension on the chain seems fine,nothing loose.the only thing i have`nt checked on the top end is to see if there was a broken inner valve spring which i doubt.i`ll upload a short video i took of the noise to youtube and post the link,again,cheers for allyour input on this.
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video link https://youtube.com/shorts/bnGOP-TrCN4
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A few strange noises going on there. It sounds 'tappety', almost like a chipped tappet or misaligned or something that's not allowing it hit the top of the valve stem square on.
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nursejulie thats my thoughts too,i was so sure it sounded like a very loose tappet,or damaged shaft,another member wrote about a 400cc having side movement at the tappets even though that bike has springs to help prevent sideways movement,up close,some of mine look nicely rounded off but others have slight imperfections,almost pitted,not sure if that could cause it.my tappets have a lot of sideways movement im thinking putting shims in there might help.im still positive its related to the rocker gear somehow.
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Well the engine is a bit noisy and has some rattling, it’s already been said but are you sure that the exhaust gaskets are not blowing a bit or even a bit of a blow on the cylinder head gasket.
At the moment we are all chasing shadows, so I feel you need to go back and systematically go through the problem. Every part of the engine has a specification with a + and - tolerance, which is listed in workshop manual. So you need to check the components which might create a top end rattle are within tolerance. For example side float on the rockers has a tolerance listed, check them with a feeler gauge, if they are in tolerance then that’s not the problem. If they need shimming then the difference between the listed specs and the actual gap will be the size of shim you need, you can’t make them tighter than the specified end float, or they will wear away at the head. You need to keep the rocker central to the valve stem, so need to know which side to put the shim, or do you need a half width shim on each side?
What I would say is strip the top end then go through all the components:- bore wear, piston wear, piston ring wear, small end wear, big end wear, all components related to camchain tensioner, cam lobe wear, cam bearing wear, engine valves, valve spring length, rocker shaft wear, rocker end float, worn or mushroomed tappits. Rebuild carefully , check engine timing, check ignition timing, put new spark plugs in. New gaskets and seals. Balance carbs.
Then hopefully post video of beautiful sweet running engine 😄.
Well that should work but there ain’t no certainties with old engines.
BTW I am certain I will have missed something important from that list so please add.
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Cheers for that Murf,its certainly in depth,and gives food for thought,im gonna step away for a few days n get some fresh perspective on things,i`ve got two bolts de-threaded now inside the top breather cover probably due to amount of times i`ve had it apart in last few weeks,so i`ll use thread inserts that i have to sort them.the bike is 48 year old but lay in a garage for 35 year so was only really on the road for like 13 year and covered around 25,000 miles,i would`nt expect to see any real wear n tear,it was running fine until recently then this noise developed so more sudden than gradual,it does have a loud clutch basket that i need to look into so the way ahead is to strip top half completely down n take measurements and renew all gaskets,do you know off hand where i could get a hold of shims thin enough i could use on side rockers? i`ll post back once i`ve had time to go through things and determine whats wrong and like you say,hopefully have it running sweet again soon ;D
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Sitting for that long can frequently cause rust spots in the bores leading to bad rings and bad piston fit
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Well after saying there were Specifications for everything, I can’t find any specs for rocker arm end float 🙁. Anyway I have had a good look at a rocker box I am going to use to replace the knackered one on my K1 550, it is the later type with the pinned rocker shafts like the one you should have.
I have checked the rocker end float:- rockers for 2 and 3 cylinders they range between .012” to .017”
For 1 and 4 cylinders they are .012”
All measurements are in thousands of an inch.
I have listed them as above because the casting in the rocker box for 1 and 4 cylinders is different to that for 2 and 3
1 and 4 have a step in the casting as shown in the photo, so clearances have to be taken on the stepped out area.
I will use this head on my engine and feel it is ok, am I right, I don’t know really, maybe someone could check the clearance on the NOS rocker box they have in their parts sash 😁.
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i should probably have honed the cylinders,i just gave them a good visual check,oiled them up and rebuilt the engine,as to end float on the arms,murf, i can certainly check n see what their at and compare to what you have.the fact the bike was running fine for the first 100 miles driven at relatively low speeds with no harsh acceleration when this fault developed,ive been looking for obvious things like damaged parts or out of place parts and not really gave thought to worn parts so as theres nothing obviously out of place i`ll need to start checking tolerances in various parts especially rocker gear.