Topic: Plugged Carb - Easy Fix?

[redbaron]

1976 CB550K. Stock airbox and carbs. Carbs rebuilt and cleaned last year.  Carb #4 is plugged. I am hoping somebody can tell me an easy fix to unplugging it.  Thanks

[flybox1]

1. Take the carbs out.
2. Clean the plugged part.
3. Put the carbs back on.
 

[BobbyR]

+1 There is no easy fix. Tried them all and wasted a lot of time doing it. Sorry Dude.

[evinrude7]

+1 take them apart.

soaking them with seafoam thru the fuel line as i did when i got the new to me bike only got me so far.  you have to bite the bullet and take them apart and clean.  even then if you don't do it with a real attempt at perfection you'll be doing it again. 

[DaveBarbier]

"taking apart" doesn't mean separating the 4 carbs from each other. Just wanted to clarify

[eigenvector]

I feel for you not wanting to remove them - that airbox really does get in the way.

[redbaron]

Hey guys thanks for the input. I was really hoping someone found a magical way of cleaning out one carb. I don't get more than about an hour a week right now with the bike and removing the carb bank and all will be a few hours.

[uksparky]

Just done my cleaning carbs in situ ..78 model 550.. pull the float bowl and pull the jets,at least its the carb on the outside, might need new bowl gasket.. mine had been sitting two years

[Deltarider]

Unsparky is right. No need to pull the rack, at least not yet. And your model carb is even easier to work on.
Did you check fuellevel in carb #4? If fuel doesn't reach the bowl and you suspect a sticking floatneedle, tap the bowl with the stub end of a screwdriver. Maybe floatneedle frees itself. If not, remove drain screw and open and close the petcock  a few times. If that doesn't work either floatbowl #4 is not too hard to remove with the rack still in situ. Here are the checks in general you could then perform. You could check if pilot jet is still in it's place and hasn't dropped (happened). Is the tiny O-ring around the mainjet still OK and does it seal well? If not, too much fuel will be sucked up around it.
All this can be done by just removing the bowl and leave the carbrack in place. Here's how to do it.
1. Unscrew the 4 floatbowl screws (I advise them later to be replaced by same size allen screws)
2. Pull floatbowl carefully downwards in a straight line.
3. Remove springleaf
4. remove float by carefully(!) extracting it's swivelpin. Do not exercise force. Some manage to break their whatever it is called (towers?). If the swingpin is hard to extract, spray some WD-40. Polish it with a bit of toothpaste. Caution: whilst removing the float, have your free hand cupped under it to collect the tiny floatneedle that will fall down. Don't loose it! They are expensive.
5. Pull the main jet using your thumb and finger. Some wiggling does it.
6. After removing the main jets twist the throttle wide open in order to raise the slides and so with them the needles. Now with your free hand insert from below a match or wooden toothpick into the needle jets (aka emulsion tubes). When that is snug in the needle jet, cant or turn the wooden toothpick a mm or so and you can wiggle the emulsion tube out easily. Some WD-40 at forehand can help. Essential in this procedure is that you open the throttle to have the needles raised. BTW, sometimes the needle jets just drop by themselves after the main jet is removed, so start with your hand cupped under it.
7. Use a small screwdriver 'slid in sideways (horizontally)' to unscrew the slow jet. Think first and make sure you turn it in the right direction. Gently!
8. Now all parts can be inspected and cleaned. Don't forget to carefully inspect the tiny O-rings that seal the main jets.
9. Install in reverse order. Do not overtighten the slow jets!
10  Install floatbowl using new little allen screws instead of the old dreadful crosshead screws. Much easier for future removals.

You need to be at ease and well concentrated. Don't hurry. Make it a Zen exercise . I can do it blindfolded and after the first time so can you.
This method can be exercised with 022A, 069A, 087A, 627B, 649A carbs.


 

[Scott S]

Hey guys thanks for the input. I was really hoping someone found a magical way of cleaning out one carb. I don't get more than about an hour a week right now with the bike and removing the carb bank and all will be a few hours.

 Removing the carb bank can be done in 15-20 minutes. It's the cleaning and bench syncing that takes a little longer. And if your air box boots are stiff, try soaking them in hot water or just get new ones for less than $40.

http://www.classicmotorcyclesolution.com/

 Loosen the clamps on the manifolds more than you think you need to for reassembly. I like to install the center two air box boots and clamps (also really loose) and get the air box plenum on the carbs and the clamps semi tight. With new boots, you can squeeze them and put the outer two boots in place once the carbs are back on the bike. Back the screws all the way out of the clamps, spread the clamps open and over the new 1 and 4 boots, tighten everything up. Don't forget to line up the nipple on the outer boots to the dot on the air box!

[Deltarider]

As the problem is with carb #4 only, no need to pull the rack with the risk of damaging the boots and what not. With these oldstyle Keihins all maintenance can be done with the carbrack in situ. It was shown to me in 1980 by a mechanic of the AA who owned one himself. I'd prefer his/my method. Removing floatbowl and fitting it: 5 mins. max.

[Scott S]

 Especially since it's #4, one of the outer ones. If it was an inner bowl, I'd pull the carbs before fighting that! FWIW, I've changed needle clip position on a set of PD carbs on the bike before. Fiddly, but doable.

[uksparky]

I had dirty main jet 1 and 4 yesterday...cleaned second time...i watched what a guy did to his cb750 on you tube...so last night i decided to do this....float bowls drained...remove tank, using another fuel hose fill bowls with seafoam....crank over few seconds giving throttle, sucking seafoam into engine..Let it sit overnight, drain bowls, fit tank and fuel line........engine ran smoother than before....           

[DaveBarbier]

If a jet is clogged from years of sitting, seafoam isn't going to do it. Mechanical cleaning with a wire with heat and carb cleaner will.

[redbaron]

Again thanks for the comments.  I will be back at it this evening and will try to clean #4 while it is still on bike.

[drumstyx]

Just done my cleaning carbs in situ ..78 model 550.. pull the float bowl and pull the jets,at least its the carb on the outside, might need new bowl gasket.. mine had been sitting two years

Are the '78 550 carbs like the '78 750 carbs? Bowls held on with screws? If so, I never understood this sort of mentality -- it's far harder to cleanly remove those screws in place than it is to just drain, pull, and do it on the bench. Not to mention, all the gunk under there and around the engine area, who knows how clean the sealing surface is, or what gunk you knock into the bowl as you're positioning #2 back in place etc.

[DaveBarbier]

Just done my cleaning carbs in situ ..78 model 550.. pull the float bowl and pull the jets,at least its the carb on the outside, might need new bowl gasket.. mine had been sitting two years

Are the '78 550 carbs like the '78 750 carbs? Bowls held on with screws? If so, I never understood this sort of mentality -- it's far harder to cleanly remove those screws in place than it is to just drain, pull, and do it on the bench. Not to mention, all the gunk under there and around the engine area, who knows how clean the sealing surface is, or what gunk you knock into the bowl as you're positioning #2 back in place etc.

How dirty is your bike? Haha

[redbaron]

I dropped #4 bowl and after closer inspection, the float needle was not dropping down enough to allow gas to flow.  I adjusted the "stop", the float needle dropped further down, the gas flowed, and the bike runs great. Thanks

[DaveBarbier]

There's a spec on the float height (within a millimeter or two) where the float needs to be. Just arbitrarily bending it is not the way to go.

[redbaron]

Thanks Dave I found a youtube video from Mike Nixon which shows this in detail.  If the bowl fills and does not overflow does it make a difference?

[BobbyR]

Dave is correct. Try using the clear tube method if possible to check the fuel height in the bowl.

[evinrude7]

it's always a bonus not to have to remove the carb rack. 

[DaveBarbier]

Thanks Dave I found a youtube video from Mike Nixon which shows this in detail.  If the bowl fills and does not overflow does it make a difference?

Yes, it does make a difference. Along with jets the fuel level in the bowl affects mixture. Float height is measured with the carbs upside down* from the bowl gasket surface to the top of the floats. So the larger the number the less fuel is in the bowls, makes sense? The less fuel in the bowls, the leaner the overall mixture. The more fuel in the bowls the richer the overall mixture.

You can set it to factory specs and you should be good, but if you have aftermarket float needles that number gets thrown out the window. A way to verify for sure what the level in the bowl is is by using the clear tube method. Google "clear tube method SOHC4" and you'll find out what that is.

*when I say upside down, there's a certain way to tip the carbs to do it so you don't compress the float needle and get a false reading. That may have been covered in the video you watched.

[drumstyx]

Just done my cleaning carbs in situ ..78 model 550.. pull the float bowl and pull the jets,at least its the carb on the outside, might need new bowl gasket.. mine had been sitting two years

Are the '78 550 carbs like the '78 750 carbs? Bowls held on with screws? If so, I never understood this sort of mentality -- it's far harder to cleanly remove those screws in place than it is to just drain, pull, and do it on the bench. Not to mention, all the gunk under there and around the engine area, who knows how clean the sealing surface is, or what gunk you knock into the bowl as you're positioning #2 back in place etc.

How dirty is your bike? Haha

It doesn't matter how clean your bike is, if you get a single grain of dirt on the sealing surface, it's going to drive you mad, because you'll have seeping fuel out of nowhere. Not to mention that, on the '78 750, there's no way you're getting the o-ring to seat right unless it's been drying for a day, or you can see what you're doing (which you can't do with the carbs in place).

But besides all that, all that bending over and frustration with it being a tight space, and stripping screws because you can't get good leverage up in there to keep the ratchet in place. I dunno, just doesn't sound like fun to me. Removing and replacing carbs builds character anyway

[DaveBarbier]

Removing the carbs from the bike isn't the easiest thing in the world, but it's not that hard. I suggest learning how to do it and cleaning the carbs properly, setting float height by the book, doing the clear tube method on the bench in a little rig (maybe the carbs mounted to a 2x4 in your vise) so you know the carbs are perfect before you reinstall.

Some things are harder than others to do on these bikes, but nothing is impossible. I'd rather learn how to do it to get more knowledge on how the bike works so you know you have a great running bike. Worst case you fiddle with the carbs while still on the bike, clean them up alright and then in the end it still not might run right but you're too lazy or nervous to do the job right so you live with it.