Topic: 76' 550CB carb thoughts to get all burning the same

[jjc]

I'm getting confused.
 I guess it's the 4 carbs that are doing it. I have a vacuum gauge and balanced all 4 carbs. But I find 1&2 are running a tad rich and the right bank / 3&4 are running a tad lean. Normally I'd reach for the main jet but all have the same jet. All have the same jets. So going to the piolet jet would adjust the mix but only until the main kicks in and then as the main kick in the piolet is fading out. Yes there is overlap. So if they are balanced and the jets are the same the only thing I have left is the piolet. I could open the right a bit and close the left hopping for things to smooth out.
Thoughts???

[denward17]

Could also be the jet needle set (needle and emulsion tube).  Do you know if the stock Honda parts are in the carbs?  What position is the clip in?

Are these 087A carbs?

[HondaMan]

How snug are the O-rings on the mainjets? If they are not the right-sized Orings, then the too-skinny ones will leak unmetered fuel right past them. This would be the 2 darker sparkplugs.

[newday777]

I'm getting confused.
 I guess it's the 4 carbs that are doing it. I have a vacuum gauge and balanced all 4 carbs. But I find 1&2 are running a tad rich and the right bank / 3&4 are running a tad lean. Normally I'd reach for the main jet but all have the same jet. All have the same jets. So going to the piolet jet would adjust the mix but only until the main kicks in and then as the main kick in the piolet is fading out. Yes there is overlap. So if they are balanced and the jets are the same the only thing I have left is the piolet. I could open the right a bit and close the left hopping for things to smooth out.
Thoughts???

Did you put in carb kits, new brass jets? Brand?

[Deltarider]

I'm getting confused.
 I guess it's the 4 carbs that are doing it. I have a vacuum gauge and balanced all 4 carbs. But I find 1&2 are running a tad rich and the right bank / 3&4 are running a tad lean. Normally I'd reach for the main jet but all have the same jet. All have the same jets. So going to the piolet jet would adjust the mix but only until the main kicks in and then as the main kick in the piolet is fading out. Yes there is overlap. So if they are balanced and the jets are the same the only thing I have left is the piolet. I could open the right a bit and close the left hopping for things to smooth out.
Thoughts???

What a coincidence! I experienced the same with my carbs (CB500K2-ED). Two months ago I have tried to achieve a CO of 4-5% at idle with an old exhaust gas analyzer I had repaired. I managed on carbs #3 and #4. When I put the sniffer pipe in the #1 or the #2 exhausts however, I had to turn the corresponding airscrews to 2¹/₂ turns out to get there, but after 30 seconds the mixture would become overrich anyway. Maybe such a device is not suited for a '125cc' engine. Also it was a consumer product for amateurs, far from professional equipment and my expectations were not high to begin with, as a Gunson tester of that same era also had performed poorly in a test by the AA and so got bad reviews.
Anyway, first thing you, jjc, should check if the fuel flow to #3 an #4 is OK and not impeded by kinks or a down and up fuelline and/or inline fuel filters. Please report back.
Maybe I should try to equalise mixture at say 2000rpm and just accept what it will result in at idle. Have any of you tried this?

[jjc]

Completely rebuilt by me. All have the same settings. Fuel lines are clean, clear.all balance at idel.
I'm ready to change the settings for the pilot jets on the lean bank and let the rt back burn a bit rich for now
I'll run with the new settings and then go back for the 6th time into the carbs

Get back to you after that.

Fyi
I have put in new coils and will see what that does

[jjc]

OK
New coils,wires, resisters.
Went through the carbs checking everything per comments. Changed main to 110 & raised needle to one up from last notch. Set bowls to 22mm per book.
Starts faster & reves cleaner. Next take it out and chack the plugs.

[denward17]

OK
New coils,wires, resisters.
Went through the carbs checking everything per comments. Changed main to 110 & raised needle to one up from last notch. Set bowls to 22mm per book.
Starts faster & reves cleaner. Next take it out and chack the plugs.

So your needle clip was in the center of 5 slots?  And you moved the clip up 1 position to slot 2 (counting down from top)?

Do you have stock needles?  Is there a number on them?

[jjc]

No
I moved the needle up. Placed it in one up from the bottom notch
Stock needles

[Mark1976]

No
I moved the needle up. Placed it in one up from the bottom notch
Stock needles

Some questions, cb550 k or f? Stock engine? Stock exhaust or aftermarket? Did you clear tube to verify a consistent float height? Are you syncing on the side stand or center stand? Using kehin brass or aftermarket? If 2 cylinders are running rich and 2 are lean and ya got fuel equally going to all 4, your not going to fix it by changing mains or pilots. Something's not adjusted or set properly. Thus all the questions...