Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: alexdecker on August 01, 2026, 09:19:01 AM
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Hey all
This is my CB550F2 from 1977 idling. Does this sound okay to you?
https://www.youtube.com/shorts/xxPyy_B_-Uw
- Alex
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Sounds ok,
Possible one cylinder out of sync
Have you checked tappets
Used a carb vacuum gauge system to do the balance
But it seems smooth and reliable
Sent from my SM-A546E using Tapatalk
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As you have asked the question I suspect the engine clatter is louder than it was at idle?
I'm no expert btw, It sounds to me as though there is a miss match at lower revs between the pairs of cylinders.
I would be checking the timings for 1/4 & 2/3 if you still have points, plus the valve clearances, then carb balance.
There are members here whose views will be backed up by decades of experience that should help.
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As John has already suggested the carbs are most probably out of synch.
Once corrected you will have smooth and nice idle.
I use Morgan Carbtune.
https://www.carbtune.com/ (https://www.carbtune.com/)
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As already noted, needs some adjustment to better optimise running.
I agree with Ted's impression, that it sounds like a pair of twin cylinders slightly out of harmony, and his advice to make sure the ignition is accurately set for both points.
Notice it sounds a little a horse cantering with that four beat rising and falling.
Carburettor synchronisation a suspect, but if ignition is out there's no point in trying to synchronize the carburettors first.
Verify the ignition setup is accurate, then look at carbs.
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Where in the UK are you Alex? Maybe someone local to you has some vac gauges if you haven’t.
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1. Always check ignition first. I recommend to have 1+4 and 2+3 breakerpoints at the same dwell or, if you use feeler gauges, the same gap as close as possible. Then check the timing. When needed, repeat procedure.
2. Sounds to me a synch will bring improvement.
3. I recommend an idle at 1200 rpm.
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Nobody seems to have asked the question, what have you done to it? Has it gone that way slowly as the mileage grew higher? Have you recently done some work on the engine and that’s the result. If so what work. My first impression was it wasn’t fully chiming on all 4 cylinders. When you rev it slowly you can hear a slight hesitation around 2000 revs, when you rev it hard it’s harder to spot that. Seems to be better at higher revs than lower. Could be a slightly blocked idle circuit or just bad timing, points or electronic? No one has asked. Points wear, electronics don’t tend to, set them up correctly and they should be fine. When you approach the bike I can hear a noise like an exhaust gasket blowing, has it been off recently? Are all the nuts still tight?
It doesn’t sound that bad tbh, phones always tend to make them sound more clattery than they are in real life. It doesn’t sound that bad a little flat so I suspect carbs more than anything else.
The idle speed is 1000rpm, if it ticks over fine at that speed the engine is normally fine. Just turning the idle speed up is like turning up your car radio because the big ends are knocking, it cures nothing, just disguises the problem and ends up costing you more in the end.
Try and see what the engine sounds like when you rev it really slowly, it highlights the problems more. I suspect it will sound worse around 2000 than at tickover, sort of hesitant and uneven.
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Sounds like a bit of clutch basket rattle. Take the dip stick out and have a listen.
Regards
Dave
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For some reason the 550 seems to be worse than the 500 for that. They both use the same shim system but tbh most people don’t even know that’s there. However the damper rubbers which hide inside the clutch basket seem to deteriorate faster in the 550 than the 500. I’ve taken 4 550 baskets apart and 3 were knackered, of the 3 500 baskets I took apart the only1 was knackered. Not sure why that is other than the drive gear being different between the 2.
They are replaceable but it’s very difficult to find a source of the rubbers.
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Thanks all for the replies!
I just switched all the boots on both sides of the carb and this was the first time I ran it. I noticed small swings in the idle, but wanted to know how this was as a baseline. I will probably do a complete maintenance with cam chain, valve adjustment, timing and vacuum sync. Just figured I might not need it if it was only the boots I had changed.
An idle that goes up and down, is that also a vacuum sync, or is that something more severe like an air leak?
I actually hadn't thought about any strange knocking noises. The primary chain is new, but whenever it idles and I don't have the clutch lever pulled, it always rattle a little more. Just figured that was the nature of the beast. But with your comments here, I might have to look into the clutch plates or springs or anything else?
- Alex
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The clutch rattle is usually a combination of worn rubber dampers in the clutch, a bit of slop on the primary chain and amplified by any imbalance in the carb sync or other effect that means each cylinder is not producing the same bang as the one next to it. From idle, rear brake on, in gear, Then let the clutch bite a little, normally quietens down at that point.
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Vac sync is the LAST thing to do after tappets, points gap, timing and cam chain.
UNLESS the carbs have been played with doing a full service normall puts the carbs within tolerance, i think Ken will confirm that!
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Alex did you change the orings in the manifold brackets? A good old mucking around getting the carbs back in and out could disturb the vac settings, doesn’t take much. As Bryan says if nothing is disturbed it should go back to it’s last settings but I’d check them just in case. Also as Bryan says, last thing you do after all the other maintenance items.
As for the clutch, there is inbuilt end float on it. You’re supposed to pull the basket along the shaft and see how much it moves before the circlip stops it. You then shim the excess away. If that’s not been done the basket moves back and too along the shaft and can create noise. It goes away when the clutch lever is pulled as that loads up the basket. However, as time goes by another factor comes into play that never really reared its head in the past, the basket damper rubbers. They are like the rubbers surrounding the rear wheel cush drive, the sprocket carrier. Except Honda never meant for the clutch ones to be changed. They go hard and brittle and start to crack. That allows the large gear bonded to the basket at the back to move, when that does it creates all sorts of noise and the clutch take off from stationary gets jerky or snatchy as the gear is just rattling back and too. The only cure for that is a new basket or to replace the rubbers with new ones. Doing that is difficult and tbh beyond most members on here. Much better to just replace but it’s finding a basket that hasn’t got bad rubbers. If you remove the clutch case you can do a quick check on the state of the rubbers by just locking up the gear wheel with a screwdriver between it and the primary gear. Now grab the basket and try and move it, both in and out and from front to back. In and out, shims, front to back, rubbers. It should be virtually solid. Best done with the basket in your hand tbh but a quick check will confirm whether you need to dismantle the clutch. If you do, fit a new circlip, don’t reuse the old one.
I recently sold a good 550 basket to another member who’s basket was knackered, I may have another, not sure. I have quite a few 550 clutches lying about. Oh and if you look for a new one don’t think the 500 basket will fit, looks almost the same but it won’t fit. Oddly the damper rubbers will but that involves some major surgery of the basket and it’s not for the faint hearted.
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Not sure if he still makes them, a former member here Max made a batch of cushions for the clutch baskets he also supplied either a repair kit using screws to replace the original rivets or would offer a fitting service. He is on eBay, I'll post the link to his shop when I'm on my PC.
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400 only Ted, 500/550 different shape. I only know of one supplier and he won't post to the UK.
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400 only Ted, 500/550 different shape. I only know of one supplier and he won't post to the UK.
I think he made a few 400 ones either to order or in small batches, I see Centurian sell them for the 400 so I think you are right.
He does some 500 & 550 spacer parts still.
www.ebay.co.uk/sch/i.html?_trkparms=folent%3Ahay_2506%7Cfolenttp%3A1&_trksid=p3542580.m47492.l71970&_ssn=hay_2506
Centurion www.ebay.co.uk/itm/126575581696?chn=ps&_ul=GB&mkevt=1&mkcid=28&google_free_listing_action=view_item
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I have sent a question asking if they do 500/550 ones, we will see
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Doubt it Bryan, if they did they’d be listed I reckon. Plus I don’t personally think their solutions of countersinking the back plate is a good one. The plate isn’t that thick and countersinking it just weakens it in that area. Possible the plate will fracture with the stresses.
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Reply i got
I will have in the next few weeks, design is currently in progress. Thanks Brian. (mine is with the I)
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Good news. Cheaper than the other source as well but not by much. Going off his other prices that is.
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400 only Ted, 500/550 different shape. I only know of one supplier and he won't post to the UK.
Will he ship to Europe though? I’m located in Denmark 😊
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Yes, he should do. I had to get a European member to buy me 5 sets just to keep the postage costs reasonable. He’s based in Germany. I’ll post a link as soon as I manage to find one. I sold 3 sets on and kept 2 sets for myself. According to Bryan we may have another source in the UK soon, let’s hope so.
Not an easy job to do Alex, I actually broke a clutch basket in 2 doing one and I’d already done one before. Sometimes the rivets are stuck solid, if you’re doing it PM me and I’ll pass on some tips oh how to avoid damaging the basket. Along with advice on bolts etc, the heads need to be very low or they catch on the gear change mechanism behind the basket.
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Hey all
So before the idling video, I had just replaced all the carb boots. I just discovered today that the intake boot on cylinder 3 was not seated properly. This might also be why the idle has a little swing.
Now, I cannot for the life of me get this boot to sit properly. It won't go over the carb, no matter how much I try. Its like its a tiny bit too short. These new boots are always so stiff and hard to handle. Any advice on how to drag it properly over the carb? It sits fine in the airbox, and the other boots seem to sit fine as well.
- Alex
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Are they genuine boots, I have it in my head that there are 2 short, 2 long with an arrow on them to assist correct fitting.
I might be confusing the 400 with the 500?
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Replica boots but specifically for the 550. Bought them off this company: https://www.ebay.de/str/acmotorradteile
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Ken or Bryan amongst others will know, was the part number different for two pairs or all the same?
Probably not listed as as a separate part from the air box.
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The carb to head boots are all the same but different length on K3, the airbox to carb are inner or outer depending on shape inside air plenum, again K3 is different
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I can't see your listing for the 550F2 in the link you posted, either way it looks as if they have possibly sent the wrong ones as F2 & K3 are not the same.
If you fit the inner pair only for cylinders 2 & 3 how does it look, are the 4 carb bodies the same part number?
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This is the direct link to the boots!
https://www.ebay.de/itm/361837356740
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This is the direct link to the boots!
https://www.ebay.de/itm/361837356740
Ok so have you checked old against new,
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Any chance you fitted them back to front? Easy done
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I've used the right boots for the intake. They are easy to differentiate, as they have the lips that go into the airbox. Unfortunately I can't measure them up against the old ones, as I chucked them when the new ones was installed in a pre-mature celebratory moment of relief of finally having done this task, as un- and reinstalling the carbs is such a pita! 🙁
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Forgot to mention, the inner 2 are sort of handed. The originals have a small tab which sticks out of the part that goes into the plenum chamber. These fit between 2 bumps on the chamber, it's to ensure you get the correct orientation. They face inwards towards each other. Plus you can remove the boots in situ. Just unbolt the airbox and slide in backwards. You can then refit them with a little difficulty but it is doable.
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Okay, this story is slowly unfolding to a grim nightmare. Got the boots fixed on all 4 intakes and exhausts, but now 2 & 3 are not firing at all.
Here is what I have done so far:
- When I had the carburetor out, I cleaned it, before putting it in with new boots (just carb cleaner, but had the top lid off and the float bowls)
- I replaced the points with new original Honda points
- I then set cam chain, valves (kept them to the looser side of around 0,08 mm intake and 0.1 mm exhaust). I then set timing.
Measured the coils and they measure a 3.2 ohm resistance each. The points are getting power. The timing is dead on. I got spark on all the plugs.
What on earth could cause 2 & 3 to just set out all of a sudden?
- Alex
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Do contactbreaker 2+3 connectors accidently make contact to the plate? Check carefully that these forked connectors are well isolated from the plate.
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Check the connectors near the rear brake light switch. You may have disturbed one. Also check the connectors near the coils. Just done a z1000 where 2-3 weren’t firing, it was the coil. Yours however is more likely to be an electrical connection issue.
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Pull the plug cap off 2/3, connect up a spare spark plug and lay it on the engine to earth it.
Turn the crank so points 2/3 closed,
Ignition on.
Open close the points with your thumb nail, spark?
Do the same with volt meter across the points, 12v open , 0 volt closed.
Where the wires connect to the points, are the insulators in the right place or have you grounded them to the points base?
Regard
Dave
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He has mentioned that he has a spark on all 4 plugs. You haven’t made the mistake of mixing up the ht leads have you? You wouldn’t be the first tbh. That normally means 2 and 4 don’t work though not 2 and 3. The middle 2 cylinders don’t share a fuel feed so it can’t be that. I wonder if the coil is breaking down under load.
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Floats stuck closed? Any fuel in the bowls?
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Oh my god, Deltarider was right on the money! Rechecked everything and was slowly going insane. After reading his comment, I was like "surely that can't be it". Went down, one of the wires on the second point had slightly moved towards the plate and was making the tiniest of contact. Cleared it, started the bike, and it went ahead and puuuuuurred like a kitten (albeit a kitten who needed a vacuum sync), firing on all four again.
Shit, these old bikes. It can be anything, but sometimes it's just the tiniest stupidest of things.
We are back! I vacuum-synced it today. Will be back with an idle video tomorrow and ask for comparison with the old one. To my ears, it sounds beautiful now. Also it revs so cleanly.
- Alex
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It is often missed, when it occurs intermittent.
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Okay, here is the original idle: https://youtube.com/shorts/xxPyy_B_-Uw?is=KRgiZOVffDpVbALb
And here is the idle now, after new boots and a full service, finished off with a vacuum sync. Best I could do: https://youtube.com/shorts/o2YUFxFuxzQ?is=LzYdFp6CxF26aIb0
Does this sound fine to you?
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It's fine now. Go for a ride, in town, minor roads and highway. Have it run at a maintained 6000 rpm or higher for some time to burn of all the carbon caused by all this idling. You'll be surprised.
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It's fine now. Go for a ride, in town, minor roads and highway. Have it run at a maintained 6000 rpm or higher for some time to burn of all the carbon caused by all this idling. You'll be surprised.
Ah, interesting! Theoretically, what can happen with the build up of carbon? I never really thought about that (like so many other things obviously)…
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Not much to worry about. Owner's ride CB500/550s often at too low RPMs. Sparkplugs face the almost impossible task to stay clean over a wide range from 1000-9000 RPM. At prolonged idling plugs tend to foul. On highways I always choose the rpm where the mirrors become clear again. Around 5000 they vibrate and the view is blurred (this can't be helped). My CB500 engine was always happiest over 6000 rpm. Try it out for yourself.
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When I am out on my 400, the expresion ride it like you stole it springs to mind.
It's like a video game, going through the gears, keeping the revs up to be on song.
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When I am out on my 400, the expresion ride it like you stole it springs to mind.
It's like a video game, going through the gears, keeping the revs up to be on song.
Interesting, I actually have a tendency to shift up all the time. For instance, shift up to 4th gear at around 60 km ph. I guess I should run 3rd gear a little longer then!
Do you have a set RPM you usually shift at?
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Not run my 500 in yet, on the 400, when in 3rd or above I like to see at least 6k revs on the clock on flat roads, on a uphill climb closer to 6500 depending on if it's feels under load. Here in the UK with 30 & 40 mph limits everywhere I'm often in 3rd or 4th.
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"At prolonged idling plugs tend to foul."
This is a direct consequence of setting idle airscrew mixture incorrectly. As noted in a recent pdf "document " of advice.
Set properly, plug fouling is all but unherad of in experience.
Advocating to run excessive fuelling when the throttle is closed has these results, along with bore wash and exhaust corrosion potential.
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Shift timing depends on conditions. Sometimes it's fine to shift at low revs, sometimes you like to amble along with low revs. The 500 is normally fine with that, if you need to pass something then shift down. Don't be fixated at only shifting at a set speed. Change when you want, listen to the engine.
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"At prolonged idling plugs tend to foul."
This is a direct consequence of setting idle airscrew mixture incorrectly. As noted in a recent pdf "document " of advice.
It's been a problem at prolonged idling ever since the CB500 was on the market. It made Honda France change the advice on which sparkplugs to use. In continental Europe the NGK D8ES-L became the favourite after break-in period, being "auto-nettoyante" (selfcleaning). This concerned the CB500, but the 550s were hardly any better in spite of 11/2 turn out for the air screws vs one turn for the CB500.
Set properly, plug fouling is all but unherad of in experience.
Then we live in different words. Already in 1980 I was warned by mechanics in the Honda workshop. It was then new to me. I have followed their advice.
Advocating to run excessive fuelling when the throttle is closed has these results, along with bore wash and exhaust corrosion potential.
Bore wash?! Bore wash does not take place where I am, with my settings. They are almost spot on with 11/16 on average. Bore wash?! My cylinders (143.000km) have not needed a rebore yet. Bore wash?! It was about sooted sparkplugs, not plugs dripping gasoline.
Besides, it doesn't need to be a problem at all, if people use their bike for the use Honda had in mind: just start and ride. If you're more the tinkering type, then you will run in sooting the plugs AND depleting the battery.
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When I am out on my 400, the expresion ride it like you stole it springs to mind.
It's like a video game, going through the gears, keeping the revs up to be on song.
Interesting, I actually have a tendency to shift up all the time. For instance, shift up to 4th gear at around 60 km ph. I guess I should run 3rd gear a little longer then!
Do you have a set RPM you usually shift at?
On the open road, 7,000 rpm is ok for fast road work
8,500 for very fast road work
These should be done several times a ride
Sent from my SM-A546E using Tapatalk
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Prolonged idling has never been advised by any manufacturer. It does happen, especially during servicing but a quick ride will clear up any problems generally. If Honda France was the only country to recommend changing grades of spark plugs you ever thought they did that because of what was in their fuel that wasn't in other countries?
Honda mechanics like most other mechanics have been known to give the wrong advice out deliberately. It depends on who they are talking to, if they dislike them or consider them either a nuisance or an idiot they'd tell them stuff that was clearly untrue. I've seen mechanics tell people that a Yamaha SR500 had points behind the rotor which ran in oil, so never needed changing. Of course it had CDI. Don't take what any mechanic says as gospel unless you know them well.
143,000 kms is barely run in. Do 263,000 miles on a set of barrels with no rebore and then you can brag. It needs one now, it's very tired these days. Bore wash is a known problem, especially as the bikes age and float levels alter as wear occurs for instance.
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Bore wash blew 1 cylinder on an Essex 3.0 V6 when the acc pump diaphram holed, and i mean destroyed the piston.
PLUS i have bored a few 500/550 cylinders recently and about 75% of these, whilst looking perfect, were actually "barrelled" in use
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They probably needed "special " spark plugs because they didn't take notice of Honda's advice in how to set mixture correctly ;D ;D
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Damn 143000 km. I think mine have gone around 83000. I actually thought that was in the higher end, and maybe the engine was reaching its end. I did a big engine job three years back, changing the shells on the crankshaft and rods, new sealings, new primary chain, top end rebuild, honing, new piston+rings etc.
How much life is normal to get out of these bikes?
- Alex
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The problem there is the honing, Honda tolerances are so tight that honing can put clearances out of spec
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I have 2 500s. The K reg is the 263000 one, no bore, same clutch. It’s had a few sets of rings, a few chains but that’s about it. The L reg one is the one I’m restoring right now, that’s done around 167,000 miles. No bore, one set of rings, new shells, both chains, new bearings but same clutch and gearbox. That still sounds like a brand new bike, great compression.
Change the oil regularly is one of the things that help them last and last. I have a nos set of barrels for this engine off a 550 but I may not use those if the present barrels are still ok.
I’m like Bryan and don’t advise honing anymore. Unless you have them under bored and hone them out to get a really tight clearance.
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They probably needed "special " spark plugs because they didn't take notice of Honda's advice in how to set mixture correctly ;D ;D
Are you really, after been able to learn my detailed report, trying to still advocate that ridiculous method by AMERICAN Honda? The same ltd, co. that has managed to never miss an opportunity to mess up, especially data regarding the CB500? What is your opinion then on p.165 in Shop Manual Honda CB500-550? Doesn't that say 022A over the left column? Ever heard of a CB500 with 022A carbs? CB550 had them, CB500 didn't.
But I'll be a sport, why don't you show us a video where you practice what you preach? I'd love to see you doing it.
@Oddjob, what's keeping you from surprising us with a vid demonstrating that you really can manage to have a CB500 idle nicely @ 600 RPM. I'd love to learn that.
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Change the record Sanitizer, I'm finding your posts tedious, & self promoting.
Are you looking to have this thread deleted? 🥱🥱🥱
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@Oddjob, what's keeping you from surprising us with a vid demonstrating that you really can manage to have a CB500 idle nicely @ 600 RPM. I'd love to learn that.
The fact that that particular engine hasn't run for over 40 years now. It's still intact but I always do the engine last in a restoration so you'll be waiting a while until the bikes ready. It may have been ready this year but after being in a coma for many weeks I lost so much muscle mass I wasn't able to walk for 6 months after never mind fix a bike. Only now a year after have I recovered enough feeling in my hands to wield a spanner. As there is no chance of finishing the 500 before winter I'll do it over winter as I'm fixing a 1976 Z1000A1 at the moment so I can get back on the road. Whether the engine will still do a 600rpm tickover is open to doubt as we now longer have leaded petrol that it used to do that on, it should but it may not.
Don't forget, having mine do it doesn't help for you to get yours to do it.
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So far it seems that Honda was wrong, the manual they published was too.
Now Honda America, same, wrong, all combustion theory , design, practice and R&D, yep wrong.
American SOHC forum, wrong. This forum, yep you guessed right, all wrong.
Mythical French mechanic, somehow is the only one that knows the secret of how to set up a Honda 500 four carburettor to run correctly. This he's passed on to the greatest interenet content SANITIZER yet seen and the greatest carburettor prophet bestowed apon this planet.
Yeh, he's bound to get no opposition on that ;D
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K2-K6, show, don't tell! Anyone can cite from a manual and be proud as a horse with two dicks. Why don't you show? Your respect for anything on paper with the name Honda on it, is troubling.
Since Karl Popper every scientist is trained to obey this essential rule: what ever the theory you put out, it must be falsifiable. This means whatever you hold for true must be open to be commented on and eventually rejected by the right way of scientific argumentation. In simple words: in science you can't say this is true 'because it's in the Bible, so end of discussion.'
Your attitude brings back the encounter we had in the southern part of the Sahara desert with a Bedouin family. We had given a young Bedouin a ride and delivered him at his family, living in a tent where the Sahel begins. We were offered tea, a ritual which takes some time, but it's seen as a insult if you refuse to accept it. BTW, you have to drink three glasses, no less, no more. It's the code. With the blue enamel kettle still in the fire, the family gathered around it and having the son as interpreter, we had some sort of a chat. After a pause the until then silent grandpa lowered the shesh from his mouth to his chin and spoke to his grandson and we noticed that the latter became a bit embarrassed and hesitated translating it. So we asked him what the old man had said.
"He asked, if we (meaning us) really believed men had walked on the moon."
Before we could have formulated an answer, the old man spoke again - just a few words - and spat in the sand as if to emphasize his words. We asked the grandson what the old man had said. It turned out the old man, before we could have replied, already had found the answer himself.
"Ällah, would never allowed it."
I'm sorry to say, K2-K6, but that's were you are.
I'm glad I have put on paper that the method you have proposed, is not doable, not on a CB500 Four. Now the road is open for anyone to demonstrate that I am wrong and that it can be done. I had expected you would have been the first. Instead of it you keep on suggesting that I'm a blasphemist. That's not very convincing, is it. You have dissapointed us greatly.
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Delta stop spouting total crap that has nothing to do with the question
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Delta stop spouting total crap that has nothing to do with the question
After you, Sir, after you.
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Life doesn't often bring compliment, bit ill accept the accolade.
"Anyone can cite from a manual and be proud as a horse with two dicks."
You may address me as "Horse" for convenience.
I'm off out to chase me some fillies ;D
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Phew, lotta heat in here :) Thanks for the input on my bike, I really appreciate it!
- Alex