Topic: Won't run without choke

[davidm]

HI again everyone -
David and his 76 cb550k saga here.

Everything was running great.  THe last thing I wanted to do this season was replaces some seals on the sides of the valve cover.  THey were leaking pretty bad.  I didn't want to ride her until I got em.    That was about 5-7 days without a ride.    They finally came in yesterday.  I put them on and tried to fire her up to check for leasks.

Wouldn't start.

Full choke and plenty of cranking and she did fire up - rough.  TYpically, I can put the choke on, start her up and then slowly back off (about 10-20 sec) the choke and she runs fine.  This time, bringing the choke back caused her to die. 

I did a search here and those sound like symptoms of clogged carbs, right?  I took them off the bike last October and inspected and they LOOKED clean.  THe PO said he had them rebuilt, but I can't be sure of what that meant.  Anyway, since then, after some adjustments and help from this lovley froum, the bike has been running really great.  So I figured they had been cleaned.

Anyway, I got a bottle of SeaFoam and Deep Creep and poured the bottle into a tank that was about 1/2 full with good clean gas.  I drained the float bowls first and the gas poured out clear. 

I know I'm probably looking at tearing the carbs down and earning that badge of a true sohc owner and rebuilding them myself.  I just was hoping some other ray of light was out there.  This is prime riding season. 

A couple of other notes. 
Spark plugs looked carbon fouled.  That I didn't expect as last I checked they were a 13/14 on Dan's MC plug scale. 
Uni filter
4-2 pipes
all else stock

Thanks everyone.  It's saturday and I have several other projects to do around the house today.  You guys are always so fast.  I'll be checking in later.

THANSK!

[flatblack]

Anyway, I got a bottle of SeaFoam and Deep Creep and poured the bottle into a tank that was about 1/2 full with good clean gas.  I drained the float bowls first and the gas poured out clear. 

I know I'm probably looking at tearing the carbs down and earning that badge of a true sohc owner and rebuilding them myself.  I just was hoping some other ray of light was out there.  This is prime riding season.

Nope, no easy way out.  The Sea Foam/Deep creep may help after a few days, but the only *sure* way to fix this is to pull the carbs and clean out the slow jets.  Shouldn't take long, though, and you can go ride.

If it helps, I've got the same problem with a CB650 and I'm trying to get them clean without breaking the carb rack off the bike.  Even after putting some carb cleaner through them, I *know* I'll have to pull them off the bike.  Just postponing the inevitable.  SSDD.

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[TwoTired]

Full choke and plenty of cranking and she did fire up - rough. Typically, I can put the choke on, start her up and then slowly back off (about 10-20 sec) the choke and she runs fine. This time, bringing the choke back caused her to die.

I did a search here and those sound like symptoms of clogged carbs, right?

Well, yeah.  At least, part of it. The slow jets.

I know I'm probably looking at tearing the carbs down and earning that badge of a true sohc owner and rebuilding them myself. I just was hoping some other ray of light was out there. This is prime riding season.
Spark plugs looked carbon fouled. 

Running on choke can easily carbon foul the plugs.

The slow jets are higher in the bowls than the mains, and starve first when fuel supply is low.  Switch to reserve and run the bike to see if your idle returns.  If not...

You don't HAVE to remove the carbs to clean the slow jets on this bike.

Were I you, I would check the head pipes while running with an idle throttle setting. The cylinders with the cold pipes have the carbs with the  plugged slows.

Then, I would catch and examine the drain off from each carb bowl in a shallow, clean pan.  The slow jets are only 0.016 in diameter.  If you find chunky bits inside the bowls bigger than this, you have to fix the source of that first.  Clean carbs won't stay clean when fed a diet of chunky fuel.

If the drainage is clean, you need only remove the carb bowls for the cylinders with cold pipes.  However, if they are carbs #2 or #3 you may wish to remove #1 or #4 bowls to easier see what your are doing to the #2 or #3 carbs.

Once the bowl is off, you can get a better idea if the carbs need to be dipped for cleaning.  If so, put the bowls back on and yank the entire rack.  But, if things still look like they are generally good then look for the short tube with a screwdriver slot in it next the large center carb body protrusion hanging down in the center of the carb.  The small tube is the slow jet.  Unscrew it (lefty loosey <<important, they break off fairly easily) blow through it and hold it up to strong light to see through it, it's not clean until you can do this.
Once clean, put it back and try to use the same amount of force to install that you used to remove it, never more.

Put the bowls and any carb bits that fell off, back in the carbs and reinstall the bowls.

Massage your wrists.  Start the bike up and ride off with teeth gleaming in the sunlight!

Cheers,

[davidm]

I decided just to pull'em off and do as you suggested, tt.  I couldn't see light thoguh them.  They're soaking in carb cleaner and I'll put it back together in the morning.

THANKS FOR THE TIPS!

[pyro139]

alot of mechanics will replace the main jets and gaskets and call it a carb rebuild. but slow jets and actual fuel passage ways in carb body would still remain dirty.

[brandon]

I recently pulled the carbs off of my 400Four to take a look at the over condition of them. I also had a leaking carb. With what the others have said, since you have them off the bike and your intent is to take them apart to clean them, simply just utilize the opportunity and give each carb a thorough cleaning inside and out. Use the manual for your bike along with an accurate caliper and make sure everthing is within specifications also. It will run much better. I promise