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Author Topic: 1975 CB550 carb lean problem  (Read 9460 times)

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Offline TwoTired

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Re: 1975 CB550 carb lean problem
« Reply #50 on: July 01, 2009, 03:44:31 PM »
I don't care what number is on your airbox, you have a K model frame (K1, actually if it is truly a 1975 model) with standard 022A carbs.  022A carbs have #100 mains and #38 slows from Honda.  If you have a #68 or a #98 main, then that explains why it is running lean.  Only a true F model with its more restrictive muffler needs that #98 jet size.

If you are using a stock, clean, air filter, then put the needle at the 4th groove from the top, Use #100 mains, sync up the carbs, and go enjoy the ride.

Is this a US Model bike?  Or, one of those European ones with that snorkel/air restrictor thingy over the top of the air filter?

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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline dilbone

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Re: 1975 CB550 carb lean problem
« Reply #51 on: July 01, 2009, 05:25:24 PM »
That is also good to know TwoTired, but I already ordered the #98's...even if it isn't ideal, it has to be night and day from the #68's in it right now.

I might see if I can email these guys and switch my order to the #100's

Must be US, no snorkel here.

If I can't get the #100's would putting the clip at the 5th groove with the #98's help?
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Offline mlinder

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Re: 1975 CB550 carb lean problem
« Reply #52 on: July 01, 2009, 05:28:18 PM »
That would cause it to be too rich at 1/2 throttle and still lean at 7/8's throttle, so no.
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Offline dilbone

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Re: 1975 CB550 carb lean problem
« Reply #53 on: July 01, 2009, 05:37:02 PM »
Looks like a mute point...I got an email back already from them, they're sending out the #100's in the mail in the morning...

I can't wait...
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Offline mlinder

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Re: 1975 CB550 carb lean problem
« Reply #54 on: July 01, 2009, 05:56:07 PM »
That's very good :)
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Offline dilbone

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Re: 1975 CB550 carb lean problem
« Reply #55 on: July 01, 2009, 06:13:40 PM »
Not sure what rules are on this forum for things like this, but
these guys are worth a look for some select parts you might need.

No affiliation, just took care of me and thought I'd give them a shout out.
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Offline TwoTired

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Re: 1975 CB550 carb lean problem
« Reply #56 on: July 01, 2009, 06:51:05 PM »
As mentioned, the needles meter midrange throttle position mostly, and the mains are dominant 3/4 throttle and above.  However, they also feed the slide needles so there is some interaction, and could also slightly lean some throttle position between 1/4 an 3/4.  But not necessarily all.  Raising the needle as a compensation play may only help part of the throttle range between 1/4 and 3/4, and hurt another part of it.

Glad you're getting the #100s.  You should be good to go with those.
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Aaron Richard

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Re: 1975 CB550 carb lean problem
« Reply #57 on: July 02, 2009, 06:21:42 AM »
you should be all set with #100's. good luck!
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Offline dilbone

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Re: 1975 CB550 carb lean problem
« Reply #58 on: July 07, 2009, 09:19:42 PM »
The #100 jets came in the mail today.

I just got them put in, buttoned it back up, and took it for a test drive after re-setting the air mixture screws.

WOW is all I can say.  Before, it was running like a scooter with those tiny little #68's in it, now it is running like a real bike.  I guess I shouldn't be surprised with an increase in main jet size of 50%!!!!!!!!  The best $14 I will have ever spent on this bike!!!!!!

It reminds me of the suzuki marauder I had a while back...it was an 800cc chain driven v-twin and this cb550 feels very similar as far as power and snap.
I am very, very pleased with this bike...I wouldn't have been able to figure this out without everyone's help and suggestions here.  Who woulda thunk that drastically wrong jets were the culprit of this severe lean problem and not just gummed up carbs from a bike that had sat for at least 5 years.

I'd still like to find out how in the hell #68's got in there to begin with...if it was that way from the factory wouldn't someone have noticed it wasn't right?
If someone did a carb re-build on 'em wouln't they have noticed it was worse after than before?  Oh well, it's all good now...

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