Topic: '77 CB550F Air Mixture Screws?

[pangea]

Hey Everybody,  long time follower, first time poster.

I'm from Maine and the riding season, for me anyway, is just getting under way here.

I have a couple quick questions that I can't find quick answers to. 

First, here's a short summary:

I'm in the process of tuning the stock (069A) carbs on my '77 CB550F.  I bought the bike a few years back and did a major overhaul of the entire bike to get it into running condition.  I've ridden it for several years now and it's always idled (mostly) fine but I'm thinking that it runs just a touch too rich at idle.  I know these bikes are engineered to run rich at idle due to the lack of an accelerator pump but I think mine might be a hair too rich.  It starts fine usually but after a sufficient warm-up period it is a little "laggy" from 0-1/4 throttle at which point, when the mains kick in, I get the acceleration I'm expecting.  It also smokes a little (white-ish smoke) from the tail pipe at idle.  It's never so bad that I can't ride it, but it's a nuisance.  It has stock 4-1 exhaust and air box and filter. 

Jets are of a stock size (I replaced all non-stock jets when I did a rebuild) but did not ever change out the air mixture screws.  I went to adjust them today and for #$%*s and giggles decided to remove them all and compare to make sure they were at least the same because I had forgotten what they looked like since I haven't had them out of the carbs for a few years.  3 of 4 of them were stock (http://www.cmsnl.com/products/screw-seta_16016390004/#.VUKW8UKDTAM) but the odd one out has a hollow tip and a hole through it perpendicular to its length.

My over-arching question is: can this possibly be the source of my problem?  Seems unlikely but   

My specific questions are: does anyone know a source for these screws that won't charge me 27 euro for shipping? I'm thinking I might just buy a rebuild kit that has this screw included because it'll be far cheaper than the shipping cost to get one screw here from overseas.  I can't find any other source for these, unfortunately. I have tried eBay, bike bandit, serius consolidated, and a few others I think.

and: are there o-rings that accompany these screws in their orifices?  I tried to look at an exploded parts view of these carbs but the quality was a little sub-par and it wasn't clear whether or not these need o-rings.  I've read a few accounts of people alluding to o-rings but I want to be certain.  For the record, mine did not have o-rings.

Hope y'all are doing well and thanks!

[Duanob]

First off did you do a 3000 mile tune up? As far as the carbs go, it sounds like you need to do a more thorough cleaning. If you never looked at the air mix screws then you never removed them? Every orifice and passage way needs to be clean and clear. Take some guitar strings, carb cleaner with a red straw and canned air and go through it again. If you have access to an ultra sonic cleaner then use it. Also make sure your rubber couplers and orings between the intakes and head are in good shape with no vac leaks. The 550F should not have a rubber oring on the air mix screws. Make sure your jets are clean especially the pilots and emulsion tubes. Make sure your needle jets are clean as well. Do a bench sync, set everything to stock OEM specs (there is a chart somewhere on this board), and install. Once running do a vac sync and you should be good to go.

[pangea]

Thanks for the reply! 

No, I have not done the proper 3,000 mile tune-up.  I set out to at least start that today.  Got as far as valve clearances and checked the timing and points gap.  I adjusted all valves to factory spec of intake to .002 and exhaust to .003, after waiting for the engine to go cold.  Several were tighter than spec and some local enthusiasts insisted that this could be the culprit. 

What do you think?  Could tighter valve clearances cause a little smoking once at running temp?  They're line of reasoning was that the valves can't seat properly if they're adjusted too tightly.

When I cleaned the carbs the first time I did use guitar string to clean every orifice.  I made sure I could see light through all of them before reinstalling.  I had forgotten about the unmatching set of air screws because my rebuild kit didn't come with replacements so I stuck the old ones back in (after cleaning them up pretty) to see how it would run.  Admittedly this was a couple years ago but I definitely made sure to dot my I's and cross my T's before installing back on the bike.  I followed the Honda repair manual when performing all maintenance.   

Thanks for the info re: the o-rings and the air screws.  That's nice piece of mind.

Cheers,