Topic: 1976 Honda CB550 restoration project

[epoch1984]

i got a 1976 cb550 for free and i wanted to restore it... the first thing i want to do is get  the engine running again, everything turns so its not locked up... however.. i have the sneaky suspicion  that the carborators on the bike are from a 750cc engine... how can i tell the diffrence between carbs for a 550 vs a 750? 

here is a pic... lol ill post more as i do more

[Laminar]

The carbs will have a number/letter combination stamped into the metal. Check yours against this list: Link and Reply #12 in the Carb FAQ.

[epoch1984]

thank you!  its official... this is my favorite forum now

[epoch1984]

ok, i got to looking at the carburetors, the only numbers i can find stamped onto the metal are 43aapj then a Japanese character  any ideas?

[Laminar]

Here's what you're looking for:



I believe it's on the engine side flange.

[epoch1984]

well the carbs on this one dont look quite like that. the part number is PD43A  im fairly certain belong to a 78 honda cb750a

[TwoTired]

http://www.motorcycleproject.com/motorcycle/text/specs.html

[epoch1984]

if that site is correct they do indeed belong to a 78 cb750

78    CB750A    PD43A    2    12.5    108    38    NA    11/8

 anything i can do to convert them, or do i have completly replace it

[TwoTired]

If you wish to restore, then you'll have to replace them.
If you just want to get it running, those carbs can be made to work.

Goals?

[Laminar]

http://www.motorcycleproject.com/motorcycle/text/specs.html

The carbs will have a number/letter combination stamped into the metal. Check yours against this list: Link and Reply #12 in the Carb FAQ.

[epoch1984]

long run... complete restoration.   for now... getting the damn thing to run. tho... playing with the engine... i think there is something wrong with the clutch...  when the clutch is engage, the kick start turns freely, however when the clutch is not engaged, the kick start will not budge... so i dunno if the engine is siezed up of if the clutch is just bad   the cluctch control is very very stiff btw

[Laminar]

I believe the clutch lever has to be out and the bike has to be in neutral to kick start. What did you mean when you said "everything turns." Does the electric starter do anything? Can you turn the crankshaft by putting a wrench on the crankshaft bolt?

You can find a new clutch cable on eBay for less than $15 shipped, it makes a huuuge difference.

[epoch1984]

OK!  well guys i know i kinda dissapeared for a long ass time, but here is the deal... some personal stuff came up and i had to put the project on hold.  but now that everything is fixed up i think i can work on it more regularly again.

here is what i know... the engine WAS seized up. cylinder wall  of one of the pistons was rusted up... so i drained the oil and and took the sparkplugs out (btw sparkplug socket for that thing is a #$%* to find).  then i filled all the cylinders with diesel fuel and replaced all the oil  with fuel as well.  i let it set over night and with a lil brute force the engine freed up. now it turns alto better and i think with turning it for a while it may just not need much engine work. 

the clutch control is still a lil messed up.  the lever that attaches to the engine right above where you put the oil in is very very hard to move... any ideas what could be wrong? i have to use a wood mallet to move the clutch. (cables not attatched)

as of right now, i have taken the carbs off.... killed about a dozen spiders that were still living in it.....  and took the float bowls off.... 2 on one side are near perfect with a lil build up of something on  the metal thing that sticks up, sorry about the terminology, im not a mechanic.  now on the other side, 1 is worse than the first 2...  and the last one... the entire inside of the bowl is coated in something crusty and green... and the flats do not move well.

pics of the carburetor


that's currently whats up with my bike 

[Laminar]

OK!  well guys i know i kinda dissapeared for a long ass time, but here is the deal... some personal stuff came up and i had to put the project on hold.  but now that everything is fixed up i think i can work on it more regularly again.

here is what i know... the engine WAS seized up. cylinder wall  of one of the pistons was rusted up... so i drained the oil and and took the sparkplugs out (btw sparkplug socket for that thing is a #$%* to find). 

They're all over eBay.

the clutch control is still a lil messed up.  the lever that attaches to the engine right above where you put the oil in is very very hard to move... any ideas what could be wrong? i have to use a wood mallet to move the clutch. (cables not attatched)

The lever on the case is always very hard to move. The clutch lever on the handlebars gives you a significant mechanical advantage. Now if the clutch lever on the handlebars isn't binding on its pivot and you have a new clutch cable and the clutch is still hard to disengage, then I'd start worrying. Also, it's a wet clutch, so having the proper oil in the crankcase will affect its operation.

as of right now, i have taken the carbs off.... killed about a dozen spiders that were still living in it.....  and took the float bowls off.... 2 on one side are near perfect with a lil build up of something on  the metal thing that sticks up, sorry about the terminology, im not a mechanic.  now on the other side, 1 is worse than the first 2...  and the last one... the entire inside of the bowl is coated in something crusty and green... and the flats do not move well.

pics of the carburetor


that's currently whats up with my bike 

Clean them thoroughly. I don't mean to do just enough that you think it will run.

I mean take a wire brush, a couple cans of carb cleaner, some very thin wire, compressed air, whatever you've got, and get them absolutely spotless. Even one small speck of dirt left in the carb may mean you have to pull the whole rack again and re-clean everything.

A little browsing of threads here will show that doing "just enough" and then having to clean and re-clean a few times is par for the course. Do it right the first time. A little shopping around should get you the proper rebuild kits, they're a good investment.

[epoch1984]

yea. picked me up some basic stuff for cleaning tonight i need to get the carb cleaner tomarrow, but for now i just hosed it all down with wd 40 to help.   now being that its a cb750 carb on a cb550.  if i get a rebuild kit, do i need anything special? to get it to work?

[epoch1984]

i have the carbs some what disasembled, but  i dont knwo how to seperate each individual carb.  any ideas? its on a 78 750 carb

[epoch1984]

ok, here is where im currently at on cleaning this particuarly nasty carb... the float bowl and floats and float pin is clean.   now on the carb body itself  im having some trouble  when i first started  the inside of the carb wehre the float bowl was attatched was covered in this weird hard green growth. now my all i have left is this hard white stuff  thats kind of bumpy on the inside of the carb where the floats attatch... any ideas how i can get rid of this stuff? its coating every nook and cranny inside this thing.  or if it will be fine to just leave it... the flaot bowl is spotless now

[Laminar]

I had some of that on a set of carbs I was cleaning. I'm not sure if it's buildup from the gas or if it's corrosion of the aluminum. If it doesn't flake or scale off in gasoline I wouldn't be too worried about it.

Is there a particular reason you're putting 750 carbs on a 550?

If I'm not mistaken, there's a plate that goes across all four carbs that each body is screwed into. You have to unscrew the body from the plate and poke it out through the hole. Then take off the top caps on the carbs and disconnect the throttle slide lever from the throttle rod that sticks into the top of the carb body.

[epoch1984]

the carb came with the bike. and i really dont have the correct one

[Flying J]

I doubt those carbs are off a 750. If they are true PD carbs they should have and accelerator pump on carb #2. Does it? Those are more like a set of carbs of a off a 77-78 550. Are you sure it was  a pd43A and not a PD46a?

[epoch1984]

all of them are marked 43a

[Laminar]

I doubt those carbs are off a 750. If they are true PD carbs they should have and accelerator pump on carb #2. Does it? Those are more like a set of carbs of a off a 77-78 550. Are you sure it was  a pd43A and not a PD46a?

Check the pictures - there's an accelerator pump on #2.

[Flying J]

Strange. I guess that would be nice. I wish my 550 carbs had an accelerator pump.

[epoch1984]

lol i just wish carbs were self cleaning

[TwoTired]

lol i just wish carbs were self cleaning

They are, if you constantly run only clean fuel through them, and don't let the fuel evaporate in the carb bowls.