Topic: 1975 cb550k with 069A carbs

[7]

Recently picked up a 1975 cb550k and when I removed the carbs to be cleaned I found 069A carbs on it. Per the FAQ they appear to be set up as stock 069A carbs also (at least based on clip position). Will this be a problem? Should I rejet and move the needle clip to the 022A setup that should be on this bike?

[jonda500]

The 022A setup should work - you'll need to change the needles and emulsion tubes to the correct ones too.

-069A needles are stamped 273004
-022A needles are stamped 272304 (same as 627B needles)

The idle mixture screws are also different, 069A carbs have solid ones, I think you need the 1.0 stamped type.
John

[Stev-o]

I'm interested in the 069 parts if you want to sell.

[7]

More interested in knowing if I can make it work with what I have. Am I going to do damage by running this way?

[flatlander]

you can use them but depending on your exhaust you most probably have to adjust the settings. the 069A were originally on the 550F which came with a very restrictive exhaust. i'd start with jet sizes and needle setting like for the K model then do some plug chops to see where you're at, before replacing other stuff.

[7]

Thought about this more last night while not being able to sleep. The whole reason I tore into the carbs was to try and fix a hanging idle issue I was having. The bike would idle ok, not great, but when I gave it some gas it would hang at 5K! I can drop it down with the choke or using the clutch. Once below 3k it will drop to idle. I figured it was a plugged jet or something. Everything looked cleaner than expected with no plugged passages. All back together and it idles good with good pickup so I'm feeling ok about the idle circuit. However... still hangs. Side note, carbs have not yet been synced other than on the bench.

So this is the current plan...

Drop the needle clip to position 4 (currently at 2) as spec'd for the 022A setup. Its a different needle but i'm not sure how much that will affect things. Theory being its too lean coming off the main jet so wont drop down. Someone correct me if that doesn't make sense. Then rebuild and sync to see what happens. If the hanging idle is gone/better I'll do a plug chop to see where I'm at with the main jet. The main jet wasn't stamped with a number that I could see so does anyone know of a jet size to ID chart? Couldn't find one.

Will report back. Continued feedback welcome.

[Stev-o]

Check for air leaks [with carb cleaner] on the carb boots, that could also cause a hanging idle.

[mrfish2]

Drop the needle clip to position 4 (currently at 2) as spec'd for the 022A setup.

I would suggest going to the 3rd (middle) position first, just change it one step at a time.  You also haven't said yet what kind of airbox or exhaust you have. Those will greatly affect the tuning.

The main jet wasn't stamped with a number that I could see so does anyone know of a jet size to ID chart? Couldn't find one.

Got a picture?

[Deltarider]

Check for air leaks [with carb cleaner] on the carb boots, that could also cause a hanging idle.

+1 And so can the 4 30,8mm ⌀ O-rings in between the intake manifold and the engine when they leak. Over the years they harden, become brittle and will leak. You can check this by spraying brake- or carbcleaner whilst idling and see if RPM varies. This should be checked before playing with needles and stuf (not recommended). Main jets should be #100 but #98 will do too.

[7]

Check for air leaks [with carb cleaner] on the carb boots, that could also cause a hanging idle.

I'm going to check for leaks with wd-40 tonight. I doubt there are any because I replaced orings on the intakes as well as the carb isolators when the carbs were off. Also going to check the spark advance is freely moving as has been suggested other places on here.

You also haven't said yet what kind of airbox or exhaust you have. Those will greatly affect the tuning.

This is kinda a funny story... When i bought the bike the previous owner had shoved a piece of foam into the air box as a "filter'. Seemed highly restrictive and the plugs agreed. To remedy this without trying to source a stock filter I made a flange to mount on the airbox and connected a K&N filter (RU-2810) to the back end. See pictures below. I planned to do another post outlining my research into this as well as how the parts were made in case someone wants to replicate.

 Exhaust is stock CB550k exhaust. Possible the pin holes are reducing restriction but i cant imaging its doing much. 

Got a picture?

Will look again once i remove the carbs tonight. I'll snap a pic then too.

[mrfish2]

With that air intake I can go ahead and say with 100% certainty you'll need bigger than stock main jets. At idle and half throttle it performs similarly to the stock airbox, but at WOT it flows quite a bit of air. At the very least start with 105 mains.

Edit: here's a pic of the filter and adapter plate i have. the adapter plate used to be manufactured specifically for the 550.

[7]

Drop the needle clip to position 4 (currently at 2) as spec'd for the 022A setup.

I would suggest going to the 3rd (middle) position first, just change it one step at a time.

Still recommend this? Or drop to the 4th?

Where is a good place to source jets?

[Deltarider]

 

Exhaust is stock CB550k exhaust.

Such a bike would deserve the original airintake and -filter setup but that's just me.

[mrfish2]

Drop the needle clip to position 4 (currently at 2) as spec'd for the 022A setup.

I would suggest going to the 3rd (middle) position first, just change it one step at a time.

Still recommend this? Or drop to the 4th?

Where is a good place to source jets?

jetsrus.com

Yes, I would still recommend trying the middle position first.

[flatlander]

To remedy this without trying to source a stock filter I made a flange to mount on the airbox and connected a K&N filter (RU-2810) to the back end.

wait a minute: instead of getting a stock air filter for about 20 bucks and just drop it in and be done, you thought it was going to be easier to buy a k&n that needs fabricating a holder?

[7]

To remedy this without trying to source a stock filter I made a flange to mount on the airbox and connected a K&N filter (RU-2810) to the back end.

wait a minute: instead of getting a stock air filter for about 20 bucks and just drop it in and be done, you thought it was going to be easier to buy a k&n that needs fabricating a holder?

Same could be said to everyone who puts pods on their bikes. I like making stuff and wanted reduce restriction of the intake without making it look modified.

[flatlander]

you made it sound like it was your goal to avoid buying a stock filter
if your goal was to improve flow at WOT keeping the airbox itself, that's a different story - and then you have my attention! are you planning to dyno test it vs. a stock filter?

[7]

About time you all received an update!

The bike would idle ok, not great, but when I gave it some gas it would hang at 5K!

The bench sync I did was not close and really screwing with things. Now that its vacuum synced I can actually make some adjustments. The bike would not idle properly because the at stock 1 1/2 turns out for the idle air screw the smaller 069A idle jet was making it so lean it wouldn't run. The idle screw was turned in so far that idle was 5 grand. Now at 3/4 turns out and doing better but i'm running out of adjustment. Probably going to have to bump up the idle jet to get some adjustment back. Currently idles but doesn't want to transition well onto throttle.

I would suggest going to the 3rd (middle) position first, just change it one step at a time.

Clips are now on 3rd position. I'll evaluate this more once I change out the mains (see below)

With that air intake I can go ahead and say with 100% certainty you'll need bigger than stock main jets. At idle and half throttle it performs similarly to the stock airbox, but at WOT it flows quite a bit of air. At the very least start with 105 mains.

After getting everything running decent I took the bike around the block and did a sudo plug chop definitely running lean. 105 mains are on their way.

you made it sound like it was your goal to avoid buying a stock filter

Sorry for the confusion. I had spent some time on the forum and found the stock air boxes were quite restrictive. I sourced the aftermarket filter to improve WOT performance because "She's a small engine who likes to have her tits revved off". I did this fully understanding there was a distinct possibility of needing to re-jet.

Thanks everyone for the advice.

[Stev-o]

1 1/2 turns out on the idle air screw?  What tool are you using to adjust the idle??

[7]

A flat head screw driver?

Jokes aside, I started at 1.5 turns out on the idle air screw (got that from the FAQ section) and turned in by 1/4 turns until I could semi reliabl come off idle to 1/4 throttle. Not scientific but enough to get me out on a run to test the mains. Open to suggestions on how to improve that process.

[Stev-o]

Not sure if your terminology is incorrect or you misunderstood the FAQ. 

The air mixture screws are not used to control idle, that is done by hand on the thumbscrew.  Unless your carbs are modified?

[7]

Probably just wasn't clear on what was going on and misunderstood what you were asking. Previously the idle adjust screw didn't do anything other than at first start up. I had adjusted it to about 1200 RPM. Once throttle was applied it would stay at 5000 RPM and the idle screw didn't change it. After adjusting the idle air screw to richen the mixture I was able to back off the idle screw and control the "hang".

[Deltarider]

It's not recommended to set the airscrews to reach highest RPM at idle. Although the engine will purr like a kitten, acceleration will be poor. These carbs do not have acceleration pumps and therefore need a relative rich idle for good driveability.

[7]

Ok... back again. Grad school keeps getting in the way of the important things in life.

105 mains are in. The bike is running well at 1/4 throttle on up. I'm concerned I'm still too lean. My 11:30pm WOT pull through the neighborhood didn't indicate much on the plugs. Probably didn't run it long enough for the sake of the neighbors.

Still having issues coming off idle. I believe the idle is still too lean as it really doesn't want to come up to 1/4 throttle (doesn't blubber but very very slow to throttle response) and if I let off it fast it dies. I'd like to bump the idle jet up from the #38s that are in there to the #40s that should be in the 022A set up. Anyone see any reason to go to #42s based on the air filter mod? Side note... like an idiot i didn't measure the idle jets as i intended to when I was swapping the mains. There are 3 or 4 different idle jets on Jets R Us which look similar enough. Anyone know which PN goes with the cb550 carbs so I can order them without tearing into the carbs to measure? Having a hard time finding this info.

[Stev-o]

Have you checked the fiche for the PN?

http://www.westernhonda.com/fiche_select.asp