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Author Topic: Done to death? Runs rich  (Read 1033 times)

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Offline Ace Blackwell

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Done to death? Runs rich
« on: April 19, 2021, 05:23:32 PM »
All, I have a 77 CB550F.  I rebuilt the carbs last year.  I've done the clear tube test and have it in good shape.   The issue is the bike smokes and drips black soot.   I thought it was oil at first.
The bike starts good and I can run about the neighborhood with minor smoking.  Then I'll go for about half a block with it smoking like hell.  After a while it will drop back out.   The bike seems to run pretty good but I can't really open it up in a residential neighborhood.
The plugs are new and get a dry black soot.  No oil and rarely wet.  When I put the carbs back together last year I adjusted the vacuum screws to where they looked previously per pictures I took.  I haven't synced them yet given I don't have a set to sync with.   
In any case, I've been reading up on the issue and have read things like valve adjustments are needed, alter normal feed screw settings, then the obvious syncing and vacuum settings.  So in short I'm looking on the most likely cause and first action I should take, assuming it's agreed the bike is running rich based on symptoms. 

Thanks
Ace
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Offline goodtryer

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Re: Done to death? Runs rich
« Reply #1 on: April 19, 2021, 08:02:55 PM »
77 CB550F Shop Manual supplement: http://manuals.sohc4.net/cb500/service_manual/HSM500550_17.pdf

See page 189: Air screws: 1.5 turns out (from gently bottomed out i.e. screwed all the way in GENTLY)

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Offline Deltarider

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Re: Done to death? Runs rich
« Reply #2 on: April 20, 2021, 01:10:20 AM »
When you have black smoke, first thing to check, is the air intake. Is there a forgotten cloth under the seat (partially) choking the air intake? Has the paper filter element become wet, either by water ingress or a messed up breather element under the air filter element? Could it be the air filter is at its end? In case of a foam filter, could it be you've overoiled it. When you've worked at the carbs, are the chokes still functioning as they should, or do they stay partially closed? Have you checked the little O-rings around the main jets are still in position and seal well.
BTW, I cannot imagine the setting of the air screws causing black smoke, even if they're set a full turn too rich.
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Offline Ssicbx

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Re: Done to death? Runs rich
« Reply #3 on: April 20, 2021, 07:16:38 AM »
I have a question, which way are you turning the air screw to lean out the fuel/air mixture? 
Screwing it out, leans the fuel/air mixture. 
I just went through the same thing with a CL160 rebuild as I was turning the air screw in to lean it out. (Wrong) Black plugs and black smoke from exhaust pipe. 
Also you can sync the carbs using a rubber hose, with air filters removed, place the hose in the same position at each carb and the other end by your ear.   
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Offline Deltarider

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Re: Done to death? Runs rich
« Reply #4 on: April 20, 2021, 08:54:26 AM »
Quote from: Ssicbx on April 20, 2021, 07:16:38 AM
I have a question, which way are you turning the air screw to lean out the fuel/air mixture? 
Screwing it out, leans the fuel/air mixture.
Correct. One turn is 360o. I'd start with 11/2 out. But setting may vary, when air intake has been altered and brassware is not OEM.
... 
Quote from: Ssicbx on April 20, 2021, 07:16:38 AM
Also you can sync the carbs using a rubber hose, with air filters removed, place the hose in the same position at each carb and the other end by your ear.   
Uh... is that a statement or a question? ;) If it's a statement, make a sound recording please.
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Offline Ace Blackwell

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Re: Done to death? Runs rich
« Reply #5 on: April 20, 2021, 07:05:52 PM »
Hey Guys,   Thanks.  I'll work on it this weekend.  Doesn't sound as drastic as I originally thought.   Deltarider did remind me of something, my bike doesn't have a air filter yet.  I have the boots and plastic box but I don't have the filter yet, Would this affect the vacuum enough to cause the issue I'm seeing?     
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Offline HondaMan

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Re: Done to death? Runs rich
« Reply #6 on: April 20, 2021, 07:18:56 PM »
I have not seen the correct O-rings for the mainjets in the carb kits for almost 7 tears, now. They are 1.2 x 4.0 or 1.2 x 4.1mm size. Most kits are coming with 1.0 x 4.0 because they are easy to find (and very cheap) but they WILL NOT seal the mainjet into the emulsifier mount. This makes it run very rich, uncontrollably so. If you happen to have the old O-rings, use them: if not, I may be able to help.
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Offline Ace Blackwell

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Re: Done to death? Runs rich
« Reply #7 on: April 21, 2021, 08:45:06 AM »
HondaMan, you are right in assuming I don't have the original rings installed.  I'll look at my stock to see if I still have them.  If not, I'll remember you.  Thanks.
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Offline Ssicbx

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Re: Done to death? Runs rich
« Reply #8 on: April 21, 2021, 12:08:04 PM »
Deltarider,  Back in the 70's I synced my carbs using the rubber hose, as sync cost $$. if you place the hose in the same location on each carb, you will hear the difference.  It may not be 100% but you can get the carbs real close.  When I get my K4 750 running I might try recording.
 
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Offline Deltarider

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Re: Done to death? Runs rich
« Reply #9 on: April 21, 2021, 01:17:28 PM »
I've often thought of that doing myself, just for the fun of experimenting. I would have to remove the airfilter element temporarily and then slide a rubber hose via the air filter case into the individual carb boots one after the other and then compare the sound. I mean, it is plausible, it should work.
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Offline Ssicbx

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Re: Done to death? Runs rich
« Reply #10 on: April 22, 2021, 08:48:06 AM »
Located this on the internet.  Used this method my TR6 back in the day.

http://sucarb.co.uk/technical-hif-type-carburetter-tuning-multi
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