It's alive ALIVE ALIVE!!!!!

 Whoohoooo!!  I finally got that bike working.  Finally ressurected my
CB550K.  Fuel flow problems up the yang, cleaned tank, removed old filter,
replaced replacement filter, starts on first try.

Ahhh, now I can break her in and start riding.  except one teensy
problem.... She idles at 9,000 RPM.

The service manual doesn't say much on where to start with this one, so I'm
wondering if someone can kick me in the right direction.  I'm thinking Idle
control stop, but it doesn't really say whether the screw should be in all
the way or all the way out.  But I'm expecting there's more to it than that.
My theory is that my uncle, the previous owner, didn't realize the gas lines
were plugged and so tuned it to compensate for the poor to nonexistent fuel
flow.

 
Start by checking your throttle cable(s).

Most likely problem is a damaged cable that's not
allowing a carb to return to idle.

Look at the carbs and make sure that the arm stops
are sitting flush against the idle control screws before
you do anything else.

Backing off these screws should allow the butterflies to
close further and reduce the idle speed but if it's idling
at 9000 RPM, I don't think it's a badly adjusted screw.
Sounds more like a missing spring or screwed up cable.

 

The mechanisms work, I verified that just now.  The arm is moving with
throttle twists, the stop is set so that it just barely touches the arm on
the throttle assembly.  I notice that the throttle cables were loose and
there is a bit of slack in the throttle and the action of the throttle is
weak and sluggish - but I don't know what is typical in a bike like this.
It certainly doesn't snap back like I would expect it to.  I fear adjusting
the throttle cable, I'll probably screw it up like I did my clutch cable,
but at least with a clutch cable you can start from scratch  - with a carb
you don't know what part of the voodoo spell you messed up on.

 Eigenvector wrote:


Is the #15 throttle return spring still there?

http://houseofmotorcycles.bikebandit.com/partsbandit/ShowSchematic.aspx?deptId#28266&machineId ”47



These carbs are modified slide valve carbs that will raise all four slides
better than the older style carbs with four individual cables. You need a
minimum of about 1/16th of an inch slack in the cable at the adjuster near
the twist grip.

#7 on the drawing is the pilot air screw. Turning it clockwise richens the
mixture, turning it counterclockwise lets more air get to the idle mixture so
it's leaner.

The starting adjustment on pilot air screws is around 1-1/4 turns and then
you try to get the engine to idle on the leanest setting possible with the
least amount of throttle opening.

--
Message posted via MotorcycleKB.com
http://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200710/1

 

http://houseofmotorcycles.bikebandit.com/partsbandit/ShowSchematic.aspx?deptId#28266&machineId ”47

It's images like that that make me despise carburators.

Actually, I'm sorry I should have better specified the year of my bike - its
a 77 CB550K.  It looks like they changed the carb on it.  I'm suspecting you
mean the #5 spring from this image (throttle return spring)
http://houseofmotorcycles.bikebandit.com/partsbandit/ShowSchematic.aspx?deptId#29821&machineId ”48

Yes its there, although it appears to be worn badly - still does its job
though.

I took a look at the choke, it works and doesn't retain the throttle
position lever.  I've tightened the throttle cable, which improved lever
performance but didn't make any real changes.  What about fuel pressure -
could the fuel filter I have on increase it beyond capacity and feed too
much fuel?

I guess the jets could be wiped out, in which case I'll have to overhaul the
carb <shudder>.