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 that I can't 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. 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, so 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'd need the chokes partially applied ridng the first stretched, it's indication the mixture is set too lean. Period. The models with PD carbs is another story. I don'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. Usuallya little tweaking there vcan result in a correct timing. This under the bordercondition that breakerpoints gap are within spec (0,3-0,4mm or 24,5^o-23^o 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 test the idle 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 idle circuit, usually a bloecked slow jet. In this test the change in RPM can be very little. That's good enough. Readjust the airscrew to wjhere you had it before the test. 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 idle circuit is clear.