Topic: '78 550k - yet another question

[egar]

I think I have the kill switch issue resolved. Thanks to all for your suggestions. Now, I have ordered a Clymer's but am anxious to set the carbs. I took them off and cleaned them last week, but as you recall my drain tubes poured gas on the floor. I'm told the floats are probably stuck. I tried tapping the carbs, but no luck. Does anyone know what the setting should be for the floats? I'm going to clean the carbs better this time as well. After reading the most recent postings I may not have cleaned them as well as I thought. Oh well, at least I know how to get the dang things off this time.

[Einyodeler]

If they are the correct carbs for a `78 ( PD46C ) then the float height is 12.5 mm.

[egar]

Wow. That was fast. Thank you much!

[TwoTired]

Sorry to inform you that the Clymer's won't help that much for your 78.  Your carbs are not covered in that book, only earlier models.

[egar]

Is there another one that would work? Like Haynes?

[TwoTired]

I don't think the Haynes covers your carbs either.
I only know the Honda Shop manual supplement 19 does.  If you want printed copy, you can get it from www.helminc.com.  You can get their phone number there.  You'll have to call them since they don't actually list it on their web site, though they do sell it.

Or, you can download a PDF version of the whole shop manual at:
http://members.thegeekgroup.org/~alphageek/sohc/

[egar]

Thanks, TwoTired. I don't know how you know all this great stuff!

[Tim.]

Download the 550 manuals from here:

http://www.sohc4.us/forums/index.php?topic=426.0

The link you were given has a much larger version (300MB) of the manual.  It has been optimized to 70MB or so, and the quality is excellent.  The much smaller files in the link you were given are manuals scanned at much much lower quality.

You'll never use a Clymer or Hayes again 

[egar]

Fantastic! I couldn't open the documents on the other site. They were pdf's, maybe I was impatient. It said "loading" on my screen but the screen stayed white for several minutes.

[egar]

Okay, I downloaded the pages of the carb and it doesn't look anything like mine! Now what? Also the needles inside the float bowls  have tiny holes all over their side to spray gas, but should I be able to see light through the bottom where it is slotted? I know the float measurement, but I don't know where to measure from. I may have gotten in too deep.

[Bob Wessner]

See if this pic helps. To measure the float height, hold the carb at an angle so the metal tab is juse barely touching the float valve without compressing the valve spring (I am assuming these are functionally similar to 750 carbs). Measure the height between the float surfaces and the edge of the carb bowl seat. If you need to change the height you gently bend the thin metal tab touching the float valve one way or the other depending on whether you need to increase or decrease the height. Hope this helps.

P.S. Ask anyone here, if I can do carbs anyone can. 

[egar]

Thanks, Olditmer! That neat how you edited my photo. I can figure that out now. Another couple of questions: I cleaned the needle you see lying on the ground and can now see daylight through it, so I guess it isn't solid and was block. But there is another screw right below the float set-up that I took out. There is a needle in that as well. Does that have to be set back in at a particular depth? As in a certain number of turns back out from the closed position? Also, one of the black rubber tubes between the last two carbs is split, which I'm sure must be replaced. Can I get that tubing anywhere in particular? We have a motorcycle dealership in town (Honda, Yamaha, Suzuki, Triumph) but they are morons and they overcharge me anytime I need stuff for my Shadow. This site is amazing, thanks to guys like you.

[egar]

I am carburetor challenged. It appears that I need to move the float up, but I can't tell whether my bending the tab up or down moves the floats up or down. Right now I bent it up because I figure that this will move the floats up. I thought Honda's motto was "we make it simple". I'm the only simple thing around here. Duh.

[Bob Wessner]

It is sort of awkward to explain, up/down in this instance. Think of it as if you bend the tab toward the float valve, the float will close the valve sooner (you will be increasing the float height) and less fuel will be allowed into the bowl. Conversely, if you bend the tab away from the float valve it will close the valve later (you are reducing the float height) and more fuel will be allowed into the bowl. I hope I haven't confused you.. I think I confused myself. 

Can't help much on the other questions, I'm not familiar with the 550.

[egar]

You explained it perfectly. Thanks. I was doing the opposite.

[TwoTired]

Okay, I downloaded the pages of the carb and it doesn't look anything like mine! Now what? Also the needles inside the float bowls  have tiny holes all over their side to spray gas, but should I be able to see light through the bottom where it is slotted? I know the float measurement, but I don't know where to measure from. I may have gotten in too deep.

The manual was originally written for the CB500.  Near the back of the manual are supplements to address changes over the model years.  Your carbs are covered in supplement 19.
What you are calling needles is actually your main jet and emulsion tubes. The jet needles are mounted in the slides that move up and down in the main carb bore.  There is a precision hole through the bottom of your main jet (#90,  0.9 millimeter = 0.0354331 inch) and all the holes in the emulsion tube attached must also be clear.  If your main jet is clogged, most likely your pilot jet is clogged, too (#42 or about .016 inch).  They are a smaller, shorter version of what your main jet looks like, except they are pressed into the carb bodies off center of the bowl (see page 177). If you don't get this jet and the passageways behind it clean, it won't idle well at all.  If you can't clear the slow jet system with carb cleaner from the pressurized can, you'll have to carefully pull the slow jets out of the carb body to clean them and passagways behind them, then press or tap them back into place.  It is best if you keep the same jet to body orientation when reinstalling them so they can maintain proper seal.  So, mark them in some way against the carb body before pulling.  The slow jet system is fed air from one of the air jets at the mouth of the carb (the other feeds the main jet), fuel from the slow jet orifice, is further meters by the idle mixture screw and then exists into the main bore of the carb.  This whole path must be clean.
The idle mixture screw you removed is set at about 1 1/2 turns out from seated (don't EVER overtighten this).  This applies to a bike stock in every way.  Exhaust and induction changes will effect this setting.

The float height is measured as described on page 60.  The small tang to actuate the float needle is bent to acheive the proper float height, which for a 78 model is 12.5mm.

That's enough for now...

[egar]

Twotired,
               You sure are patient with me. I found the supplemental pages and damn if these aren't my carbs. I'm going to print them out. I read your description of the different screws carefully so that I now know one from the other. When I took the carbs apart last week, I thought I did a swell job, but after inspecting everything this time around, I'm finding blockages in the main jets, dried out crap in the bowls that I missed last time around, etc. I went to ACE Hardware this afternoon, by the way, and found rubber hose that will fit perfectly to replace the cracked hose that connected two of the carbs. A foot of this only cost 39 cents. I'm starting to get creative. I can see why these restorations are addicting. It wouldn't be much of a challenge if it hadn't been a $100 bike.

[Tim.]

Just be careful about what sort of tubing you use with fuel.

[egar]

I'm really frustrated this morning. I took the carbs off again, cleaned all the jets (main jets were blocked and I didn't realize it, put it back together and it still won't run without a blast of starting fluid. I'm careful with that because I know you can blow the heads. My question: is it still a fuel problem. I adjusted the floats to the best of my ability and turned the mixture screws 1 3/8 turns like I've read about. I have not touched the points yet. My question - since the bike will run for a second on starting fluid, does that mean the points are OK? It tells me that I'm getting a spark to run it for those few seconds? I'm afraid I'll get too frustrated and stick her on E-Bay. That would be a real defeat.

[Bob Wessner]

I'm afraid I'll get too frustrated and stick her on E-Bay.

Don't do that! If you are sure the carbs are in good order now, and the floats are correct height, it could be ignition. Starter fluid is easier to ignite than fuel. Have you tried pulling all the plugs and with their respective leads on, ground them to the head while cranking the starter to check if you are getting good healthy sparks at all the plugs?

Depending upon how long the points and condensors have been in there, it might be a good time to change them out and time the ignition as well.

[egar]

I will try that, then. I have too many hours into it not to give it a shot.

[bryanj]

If the mains were blocked i will just about guarantee the pilots are too! They are those pressed in jets. You can remove them by gripping CAREFULLY with vise-grips and twisting and pulling at the same time. Clean out thouroughly and carefully then reinsert with a tap from a nylon hammer.

[TwoTired]

If you can get it to run for a few seconds with starting fluid or squirting gas into the carb throats, then it seems unlikely that spark is your issue.
The main and needle jet supply the bulk of the fuel from 1/4 to full throttle.  The slow jet system supplies the bulk of the fuel need for operation at 1/8 throttle and below.  The two systems are somewhat interactive, but dominant when they are selected by throttle position.

I'm guessing your frustration stems from lack of thoroughness in cleaning ALL of the carburetor instead of just the easy bits to get to.  Did you clean and clear the slow jets too?

Also, why did you set the idle mixture screws for 1 3/8 when the manual is clear about 1 1/2 turns out.  Further, the if fuel starvation is occurring, perhaps 1 3/4 is a better starting position.

If you already are thinking about Ebay at this point, with so little effort put into the bike, then that is probably the best route for you and where it is destined running or not.
Good luck,

[egar]

BryanJ: I cleaned the pilot jets out, too, I slipped a piece of rubber hose on them afterward and blew through them to make sure I could hear air at the other end. I cleaned the slow jets as well. Maybe I didn' set the floats rights. The whole measure-while-it's barely-touching-spring thing is sort of tricky.
Two-tired: The idle screw thing is a bit confusing. How do you know at which point to start before you turn the screws out? When the theads are not visible on the screw? It seems you can screw them in too tight (I have been warned not to do this) and then count the turns. Does that make sense? Sorry about the E-Bay comment. I was really frustrated and hot. I live in Fla and my garage is a sweatbox right now. If my mixture screws are too far out, would it fire up at all? I'm thinking about taking the carbs off for a third time and going through the whole cleaning and setting process again....

[TwoTired]

Two-tired: The idle screw thing is a bit confusing. How do you know at which point to start before you turn the screws out? When the theads are not visible on the screw? It seems you can screw them in too tight (I have been warned not to do this) and then count the turns. Does that make sense?

Just remember the idle mixture screws don't hold anything on the carbs.  Don't treat them like a screw that must be tight to hold something on.  You can feel some resistance when they are turned as there is a spring behind them.  But, when they seat the resistance goes up rapidly.  Don't force it.  Turn them back out 1 1/2 turns. It's a flat blade type and easy to count in 1/2 increments.

If my mixture screws are too far out, would it fire up at all? I'm thinking about taking the carbs off for a third time and going through the whole cleaning and setting process again....

The worst thing about turning them out too far would be that it idled too rich.  Address that issue after it is running.

When you clean them next time and feed air or fluid under pressure into a selected jet, there should be two exists for each system.  Pressure on the main jet should exit out where the main needle is seen in the carb throat AND one of the air jets at the bottom of the inlet side mouth of the carb.  Pressure on the slow jet should have an exit at the carb throat near the front of the slide AND the other air jet at the bottom of the inlet side mouth of the carb.  The air jets look like small 1/8 in. tubes.  But, they have a restriction deeper inside.