Topic: Difference between 78 550K and 76 550 carbs?

[VigCS]

Hi all,

I have a '78 550K and is (unfortunately) in need of a new rack of carbs.  I found some very promising ones on eBay off of a '76, but they look slightly different than what I have.  Does anybody know if they might work on my bike?

Here's a link:  http://cgi.ebay.com/ebaymotors/cb550-550-carburetor-honda-1976-cafe-parts-_W0QQcmdZViewItemQQhashZitem33664f490dQQitemZ220759804173QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_1055

They look very similar, but not identical.  Thanks for any input!

[TwoTired]

Direct swap carbs only...No.
Manifolds and couplers front and rear along with the air box, ...yes.
Different throttle cables too.
PD carbs have one fuel inlet, the 76 carbs have two so, you'll need a T fitting also.

You will also have to play with jetting and adjustments.

I don't know if you are still using the stock exhaust or induction.

Cheers,

[VigCS]

Direct swap carbs only...No.
Manifolds and couplers front and rear along with the air box, ...yes.
Different throttle cables too.
PD carbs have one fuel inlet, the 76 carbs have two so, you'll need a T fitting also.

You will also have to play with jetting and adjustments.

I don't know if you are still using the stock exhaust or induction.

Cheers,

Thanks a lot.  I think I'll probably just take mine apart and see why they're sticking at > 1/3 throttle.  I think I may have bent the throttle shaft.  

And no, I have pods (which I'm swapping out for the original airbox) and some brand of exhaust I don't know.  They were on the bike when I got it  (video: 

[OldSchool_IsCool]

The 78's also use a choke cable on the instrument panel rather than the lever down by the carbs.  Idle adjustment is also different.  One uses an air screw (back it out to lean out idle) and the other uses a fuel screw (turn it in to lean the mix).  I don't remember which year is which.

[VigCS]

Just thought I'd give this thread a quick update...

I started taking my carbs apart, and at first it seemed like the shaft that actuates all of the slides may have been bent.  However, I disonnected all of the slide adjuster arms from the main shaft (with the shaft still in) and the inner two carb slides went up and down without any problems.  The other two stuck really bad (lift the slides up and you'd have to push them back down).  This leads me to believe that the tubes that the slides go in in the outer two carbs were bent out of round. 

Anybody have any suggestions?  I know that the shaft still could be bent, which may be what's causing the outer two carbs to stick (even though the adjuster arms are disconnected from the shafts).  I'll be taking the shaft off as soon as I can work my way through some stripped screws holding the assembly together.  I'm currently in a bidding war on ebay for another set, but I'd love to figure out how to fix these.

Thanks!!

[TwoTired]

If you think you bent the slide tubes.  You could measure the bores for out of round. 
Or, coat the slide bores with Dykem blue (or dark felt pen.)  Then work the slides up and down to find the wear points.  The ink will wear off first, showing where the binding occurring.

Bending them back entails either finding or making a tool to put the round again.  A tool similar to an bicycle head stem might be inserted and tightened to force the tube back to round.  Making certain the wear point are where the expanding pressure is applied.

Cheers,

[VigCS]

Thanks, TwoTired.  I'll have to use some sort of marking compound, my tool selection doesn't go past the basics (socket set, wrenches, etc...).