CB550 Tuning Advice

[K2-K6]

Aah! The choke on any carburettor is described as ON when its restricting airflow by shutting off the incoming air. That's it's starting/cold position.

Choke OFF is with the restriction of incoming air least affected. This is normal/warmed up running position. 

[Neilw]

Just to make sure: when the little chokelever is horizontal the chokeflaps are down (to facilitate cold start), when the lever is vertical the chokeflaps are up (engine warmed up).

One simple question (Thank you), and now i get this :-)


https://youtube.com/shorts/rqzMJKfwX5I?feature=share

A bit of white smoke.

Haven't tried with choke on :-)

Got it idling with throttle screw adjustment.

That's me done for the day, now feeling very happy i've heard it running.

Thank you so much for bearing with me.

 

[Bryanj]

On is when butterflies close off the hole, off is when theyare horizontal i.e. hole open

[K2-K6]

That sounds really good in the yt clip Neilw.

Bang on the money for carb balance, so much so that I wouldn't change that at all.

From an interest point of view to us out here, a clip of it with gauges hooked up to show what they read would be interesting. But I'd not change the balance set you've got  .... even if the gauge suggest any variance.

Well done with tbe detailed work, very frustrating at times, isnt it? That's very good progress there that you've got too.

"White smoke " is just vapour from combustion before the cylinders and exhaust have got fully warmed through. That'll disappear when fully up to temperature, perfectly normal from cold start in engines.

[deltarider]

Now bring the rpm down to say 1150 and then let us judge the sync.

[Neilw]

Now bring the rpm down to say 1150 and then let us judge the sync.

Cold start this morning with the Choke on. Wouldn't start unless i blipped the throttle, and then would only stay running if i held the throttle open, which i did to warm up the bike.

I then switched the choke off (down position), and the bike immediately started running smoothly. I let it run for a while, it spat once or twice and then died about a min later. Started immediately without choke and idled quite happily with a few spits.

https://youtube.com/shorts/DL4JK8qOT2g?feature=share

Idling at 1200 rpm thereabouts.

I don't think i'll be taking the carbs off now, so I'm going to put the airbox back and air filter to see what this does.

Other than the throttle screw i've changed nothing - airscrew is still 1.5 turns.

[K2-K6]

It may not be cold enough ambient to need full choke at this time of year in starting it. Worthwhile trying at 1/2 to judge effect.

Many bikes of this era have no throttle interaction with "choking" application, its just down to you to open the throttle a little, as appropriate, to balance demands at this cold start phase of running bikes like this. That's entirely normal and expected.
The end of line SOHC models variously had the throttle and choke linked to give the effect that you're doing manually here.

It does sound particularly good in running and cylinder to cylinder parity. If anything, it's "hunting" slightly (a little excess fuel at that independent running point) which is detectable in minor way.
A couple of miss/stumble hiccup heard, likely to be the plugs having not fully warmed from riding out on it (typical if just standing with no load ) that should disappear when all up and running.

As you note, fully assembled intake system to be installed, then see what you've got at that point.

It is very smooth though. Any competent workshop would be proud of that result.

[Bryanj]

The 500/550 with those carbs need choke on to start but almost immediately back to half after starting and fully off fairly quickly, unless you are trying to ride in sub zero temperatures and i for one am too damned old for that!

[Neilw]

The 500/550 with those carbs need choke on to start but almost immediately back to half after starting and fully off fairly quickly, unless you are trying to ride in sub zero temperatures and i for one am too damned old for that!

Lol, this bike will only see summer temps, no cold or wet riding for me!

[deltarider]

The 500/550 with those carbs need choke on to start but almost immediately back to half after starting and fully off fairly quickly, unless you are trying to ride in sub zero temperatures and i for one am too damned old for that!

The running now, indicates there's room for improvement.
I see a tube/some tubes (?) near the carbs and breather tube which I cannot identify. What is it/are they for?
Here some tips. Fuellines need to be 5,5mm ID and the length should be 18 and 30cm for the models with the oldstyle petcock and 17 and 28cm for the models that have the newer model petcock. Use the clamp for the fuelline that feeds carb 3 + 4 (see pic). The CB500/550s are very sensitive for correct dimensions and routing of the fuellines. No ups and downs and no extra socalled inline filters, this to avoid nasty surprises which you may encounter even weeks later, when you have already completely forgotten you ever fitted them and are scratching your head in wonder what's wrong! Don't ask me how I know.
Then, the correct starting procedure is well instructed in the Owner's Manual. I've nothing to add to that. Read it and follow it up. For these models it's normal, you need a somewhat raised idle for the first one or two km after you've put the chokelever fully down. Don't be tempted to ride with the lever halfway. The lever - not being in the view of the rider! - can make you forget about it. These models were developped with Honda's extreme care for ergonomics. Honda certainly did NOT want you to take your left hand from the handlebar to blindly trying to find and fiddle with the choke lever. Chokes should be fully reopened (lever fully down) before you begin your ride. As these models have a relatively rich idle - certainly in comparison to the later K3 models - a somewhat raised idle is enough for good driveability in the first 1 or 2 kms. So if you need to stop say at a traffic light, just keep the idle somewhat raised. If you would need the chokes partially applied riding the first stretch, it's clear indication the mixture is set too lean. Period. The models with PD carbs is another story. I won't go in to that here.
I'd doublecheck the ignition just to be sure: a correct timing at full advance is paramount. If it's not, don't fidlle with the plates, but first check the breakerpoints gap. Usually a little tweaking there can result in a correct timing. This under the bordercondition that breakerpoints gaps are within spec knowing 0,3-0,4mm or 24,5^o-23^o when measured by a dwellmeter set in the 8 cyl position).
Having the airscrews where you have them now, I'd (re)sinc at ~1200 RPM. If needed you can check the slow circuits of all four by individually turning the airscrew full in, wait 20 seconds and then open 3 turns, wait another 20 seconds. If you hear no change in RPM it's indication something is blocked in the slow circuit, usually a blocked slow jet. Mind you, in this test the change in RPM can be very, very little. That's good enough. If all slow circuits hve proven functional (clear), readjust the airscrew to where you had it before the check. Repeat the procedure for the next carb. An eventual tweaking of the mixture by the airscrews can be done later. For the synching it plays no role, provided the slow circuit is clear. I've substantiated this extensively here: https://www.sohc.co.uk/index.php/topic,32847.msg320078.html#msg320078
Success!

[Neilw]

The 500/550 with those carbs need choke on to start but almost immediately back to half after starting and fully off fairly quickly, unless you are trying to ride in sub zero temperatures and i for one am too damned old for that!

The running now, indicates there's room for improvement.
I see a tube/some tubes (?) near the carbs and breather tube which I cannot identify. What is it/are they for?
Here some tips. Fuellines need to be 5,5mm ID and the length should be 18 and 30cm for the models with the oldstyle petcock and 17 and 28cm for the models that have the newer model petcock. Use the clamp for the fuelline that feeds carb 3 + 4 (see pic). The CB500/550s are very sensitive for correct dimensions and routing of the fuellines. No ups and downs and no extra socalled inline filters, this to avoid nasty surprises which you may encounter even weeks after fitting them, when you have already completely forgotten you ever installed them and are scratching your head in wonder what's wrong! Don't ask me how I know.
Then, the correct starting procedure is well instructed in the Owner's Manual. I've nothing to add to that. Read it and follow it up. For these models it's normal, you need a somewhat raised idle for the first one or two km after you've put the chokelever fully down. Don't be tempted to ride with the lever halfway. The lever not being in the view of the rider! can make you forget about it. These models were developped with Honda's extreme care for ergonomics. Honda certainly did NOT want you to take your left hand from the handlebar to blindly trying to find and fiddle with the choke lever. Chokes should be fully reopened (lever fully down) before you start the ride. As these models have a relatively rich idle - certainly in comparison with the later K3 models - a somewhat raised idle is enough for good driveability in the first 1 or 2 kms. So if you need to stop say at a traffic light, just keep the idle somewhat raised. If you would need the chokes partially applied riding the first stretch, it's clear indication the mixture is set too lean. Period. The models with PD carbs is another story. I won't go in to that here.
I'd doublecheck the ignition just to be sure: a correct timing at full advance is paramount. If it's not, don't fidlle with the plates, but first check the breakerpoints gap. Usually a little tweaking there can result in a correct timing. This under the bordercondition that breakerpoints gaps are within spec knowing 0,3-0,4mm or 24,5^o-23^o when measured by a dwellmeter set in the 8 cyl position).
Having the airscrews where you have them now, I'd (re)sinc at ~1200 RPM. If needed you can check the slow circuits of all four by individually turning the airscrew full in, wait 15 seconds and then open 3 turns, wait another 15 seconds. If you hear no change in RPM it's indication something is blocked in the slow circuit, usually a blocked slow jet. Mind you, in this test the change in RPM can be very, very little. That's good enough. If all slow circuits hve proven functional (clear), readjust the airscrew to where you had it before the check. Repeat the procedure for the next carb. An eventual tweaking of the mixture by the airscrews can be done later. For the syncing it plays no role, provided the slow circuit is clear. I've substantiated this extensively here: https://www.sohc.co.uk/index.php/topic,32847.msg320078.html#msg320078
Success!

Thank you.

The only pipes you are seeing are the breather hoses, the carb bowl overflow pipes, and the fuel hose. There are no other pipes or hoses; perhaps the cables and uncut cable ties look like hoses.
 
The fuel line is 5.5 ID, I have it clamped as suggested and will double-check the lengths.

I don't have a dwell meter, so I will try the other things you suggest to see if I can get it running a bit smoother.

Should i re-balance the carbs, as i have the kit to help me with that?

I'm a little way from being able to do a road test, so i just want to do the best I can as a good starting point. I only intend to do a few hundred miles a yr.

Many thanks and I'll go read your PDF, the vid sounds good.

[Oddjob]

Here some tips. Fuellines need to be 5,5mm ID and the length should be 18 and 30cm for the models with the oldstyle petcock and 17 and 28cm for the models that have the newer model petcock. Use the clamp for the fuelline that feeds carb 3 + 4 (see pic). The CB500/550s are very sensitive for correct dimensions and routing of the fuellines. No ups and downs and no extra socalled inline filters, this to avoid nasty surprises which you may encounter even weeks later, when you have already completely forgotten you ever fitted them and are scratching your head in wonder what's wrong! Don't ask me how I know.
Then, the correct starting procedure is well instructed in the Owner's Manual. I've nothing to add to that. Read it and follow it up. For these models it's normal, you need a somewhat raised idle for the first one or two km after you've put the chokelever fully down. Don't be tempted to ride with the lever halfway. The lever - not being in the view of the rider! - can make you forget about it. These models were developped with Honda's extreme care for ergonomics. Honda certainly did NOT want you to take your left hand from the handlebar to blindly trying to find and fiddle with the choke lever. Chokes should be fully reopened (lever fully down) before you begin your ride. As these models have a relatively rich idle - certainly in comparison to the later K3 models - a somewhat raised idle is enough for good driveability in the first 1 or 2 kms. So if you need to stop say at a traffic light, just keep the idle somewhat raised. If you would need the chokes partially applied riding the first stretch, it's clear indication the mixture is set too lean. Period. The models with PD carbs is another story. I won't go in to that here.
I'd doublecheck the ignition just to be sure: a correct timing at full advance is paramount. If it's not, don't fidlle with the plates, but first check the breakerpoints gap. Usually a little tweaking there can result in a correct timing. This under the bordercondition that breakerpoints gaps are within spec knowing 0,3-0,4mm or 24,5^o-23^o when measured by a dwellmeter set in the 8 cyl position).
Having the airscrews where you have them now, I'd (re)sinc at ~1200 RPM. If needed you can check the slow circuits of all four by individually turning the airscrew full in, wait 20 seconds and then open 3 turns, wait another 20 seconds. If you hear no change in RPM it's indication something is blocked in the slow circuit, usually a blocked slow jet. Mind you, in this test the change in RPM can be very, very little. That's good enough. If all slow circuits hve proven functional (clear), readjust the airscrew to where you had it before the check. Repeat the procedure for the next carb. An eventual tweaking of the mixture by the airscrews can be done later. For the synching it plays no role, provided the slow circuit is clear. I've substantiated this extensively here: https://www.sohc.co.uk/index.php/topic,32847.msg320078.html#msg320078
Success!

There are so many errors in that statement it beggars belief.

The 500 and the 550 are not sensitive to fuel line lengths, I've seen loads of them that have been replaced by other types of lines, braided clear lines were quite common in the 70s. They were regularly chopped by owners who broke the lines tugging them off the petrol tap nozzles, ignoring the clips Honda had fitted. If they were sensitive they'd react when an auxiliary tank is fitted, they don't. 5.5mm I'd agree with but only because it's the correct size for the fittings Honda used, no other reason. It's clamped so it doesn't have any chance of resting against the engine and possibly melting or being trapped. The simplest explanation is usually the correct one.

The worst error though is assuming you know what Honda were thinking at the time, Honda certainly did NOT want you to take your left hand of the bars?? The best selling motorcycle in the world is the Honda C50 or cub. It sold over 100 million by 2018. Maybe 150 million by today, who knows. It was designed by Soichiro Honda and the managing director at the time Takeo Fujisawa. Oddly when they were traveling around Europe checking out the mopeds in use at the time. When they returned to Japan their design brief was for a step thru frame but most important was the ability to ride the bike one handed so that the rider could carry Soba noodles in their left hand. That's true, look it up on the web if you don't believe it. So saying Honda didn't want anyone to ride one handed is not only false but a huge mistake. Riding one handed isn't that unsafe, riding with the choke half on is how most riders set off in winter time. Ever drove a 70s car Neil? one of those with the choke knob on the dashboard, you'd pull it fully out to start the engine but then sit and juggle with it for a few secs trying to keep the engine running. If you pushed it fully home and tried to set off I guarantee it would stall. You drove for a few hundred yards or more depending on how cold it was with the choke knob halfway out, then you'd slowly push it home as you drove or at some lights. Same principal.

Ignore the rest. Yes, check the sync using vac gauges. Be interesting to see how close they are. As for the rest, test ride the bike first. See how it performs, does it pull ok, are there flat spots, are the plugs fouling. You may have accidentally got everything spot on, moving stuff before you check is not advised. Check first, alter afterwards is better practice.

[deltarider]

All my posts refer to original bikes only and I don't do aftermarket parts unless they have proven good.
Both the hands at the handlebars at all times. No need for a steering damper and you will not have a tank slapper.
The rest is the usual revenge comment we got used to by now.
Can we expect footage of a CB500/550 idling nicely at 600 RPM of your hand soon or are you still finetuning?

[Oddjob]

Revenge post??? Don't make me laugh.

I post when I see others trying to advise others with information that is clearly wrong. Never mentioned aftermarket parts, I said others had replaced the fuel lines with something else, did they measure them? Did they hell. If it reached the tap they were happy. Did the bike suffer from having odd lengths fitted, no. So that advice was wrong, pure and utter drivel.

Both hands on the bars I'd agree with, when you can that is. However saying that Honda did NOT (and the capitals are yours) want you removing a hand from the bars to alter the choke is also wrong. The whole company became what it is on the principal of riding one handed. They advertised the C50 in Japan on it's ability to deliver non soggy Soba noodles, the bike was designed for delivery riders in mind. Try reading the facts instead of inventing your own. You needed an argument to say riding with the choke half one was wrong, you invented the one handed argument to support it. You argued it was Honda philosophy not to encourage one handed riding, you were utterly wrong. Just because that's the way you ride doesn't make it the correct way. We all ride differently, we all at some point ride one handed, some riders only have one arm, doesn't stop them riding.

As for the 600rpm tickover, LMAO. I've told you, my engine is the last part of a restoration I do. It would most likely have been done now but as I'm sure you're aware I got critically ill last year. Spent over 5 weeks in a coma, research what 5 weeks in a coma does to the human body. Short answer is it wrecks it. Recovery is scheduled in years not weeks or months. I'm 15 months on now from discharge and I still can't walk correctly. My hands don't work as they used to. Spanner work is possible but limited. You'll see the 600rpm tickover, don't hold your breath though. It may be another year or 2 before I get around to building the engine.