Topic: oddly running cb550f

[migopod]

My '76 cb550f is running better than it has been for a while, but i'm still having some odd
issues with it.  I checked the carb and timing faqs, but this seems to either overlap both
(possible) or not exactly fit in either.  It was running on three, until I located a broken part
in the carburetor rack and replaced it.  Now it feels flat when running at any constant speed, and kindof
feels weak and sputtery. 

Now here's the odd part.
a) unless it's been sitting for more than a week, it starts first kick (i don't use the electric start).
b) it idles very smoothly and reliably right at 1k.
c) it is very responsive to the throttle, and accelerates quickly and smoothly.

Lately i've been mostly riding in the city on short, residential blocks, so i'm usually in 1st and 2nd.   If I
engage the clutch and suddenly open the throttle, it takes off admirably, and then between 4k and 5k
(if i level off on the speed) it feels like it's missing on one or more cyls.  If i kick it to 2nd and accelerate
again, it picks up and accelerates smooth as silk again.

It doesen't seem too specific to RPM, since if i'm going slower in each gear it still feels missy and sputtery.

I have new main and pilot jets and a new dyna S ignition, which seems to have improved it
greatly from last year when it wouldn't run without the choke on full.  The needles are clipped in
the middle position, and the vacuum is set pretty closely on each cylinder.  Timing was done
static, and i'm using the stock airbox and 4 to one supersport exhaust. 

I feel really close to having it running perfectly, but i'm hoping for some advice as to what
should be tweaked first so as to save myself time and sweat.  I'm also concerned that since
it seems to be happiest while accelerating, that i'm likely to get pulled over by milwaukee's
finest.

Thanks!

[Dennis]

You say that you are doing a lot of city riding!
How is the charge in the battery? It can easily run down with this kind of riding.
A low battery could result in poor performance.

[TwoTired]

The Honda shop manual says that the needles should be clipped into the 2nd groove.  And no, it's not clear from which end to start counting.

You should be able to verify too lean or too rich by checking the plugs. Do the "plug chop test" and compare your plugs to the chart at :
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Then raise or lower the needles one position, resynch the carbs and go for a ride.

Your problem statement/description was very good.  I wish all the queries were as nicely detailed.
Sounds like with one more adjustment you'll have a happy bike with an expert mechanic.

Cheers,

[migopod]

Thanks for the info,
I expect that the 2nd clip position would probably be towards the non-pointy end and the middle one is the 3rd.
This would make sense, since the low-rpm performance improved when i leaned out the idle mixture screws, and
the plugs do look pretty sooty.

As not particularly crazy about taking the carbs out again as i am, i'll try re-clipping the needles and report back.

As far as charge, the battery is about a year old, and trickle charged overnight.  The 3ohm coils might hit it a
little harder than the stock ones did, but usually the headlamp is pretty bright when i'm done riding.

Also, would it be worth also getting a timing strobe (i see sears has one for about $34), or is static usually good enough?

[TwoTired]

Years ago, I re-clipped needles on my 74 CB550 while the carbs were still on the bike.  However, I know the F model frame is different.  So, I can't say for sure you can do that on the F model Frame.

The static method is fine for new points.  But, when they get old, a timing light is a bit more accurate.  Plus, you can then check your advance timing.  I have atiming light.  But, I usually just static time the points and file them when they look too rough.

[Dennis]

You're probably ok on the battery, but I'd check it if you continue to have a problem. Stranger things have happened.
I think that you are probably correct on your interpretation of the location of the needle, but as LLoyd says they really don't say. Lowering the needles if they are sooty would be the thing to do, I had to do that on my 750F.
As far as timing, I'll generally static time them with a beeping continuity tester (on my Fluke meter) so I don't have to watch for a light. If I'm not feeling too lazy I'll fine tune and check advance with a strobe light.

[Gordon]

To correctly time the Dyna-S ignition you need a strobe light.  It's timed at full advance rather than at idle speed.