Topic: '78 550 carb difference question

[tomasz]

greetings,
I currently run my '78 motor with a set of '75 carbs but I have a set of '78 carbs that I just rebuilt and plan on bolting onto the engine; so I have noticed some design differences: choke is completely different, the tops are different and access into the chambers and needles appears to be easier; are there any other issues I should be aware of, will the earlier cables will work with this one ? I haven't tried mounting it yet. thanks, tomasz

[migopod]

the 78 carbs will have to have different cables and intake manifold for sure, and the 78
will probably need a choke cable.

When i put 77 carbs on my 76 supersport I also had to abandon the stock airbox
because the carbs + manifold were too long to fit (ended up using pods).  Also 77 and after carbs use one
fuel inlet instead of two.  Other than that, both 76 and 77 carbs seemed to function
equally well.

[tomasz]

i use pods now so that shouldn't be a problem, i see the fuel inlet right in the middle of the second carb but what is the other one, air port of some sort ?

[TwoTired]

Yep, you guessed it.  The float bowls need an atmospheric pressure vent.  The original bike had tubing there that went down to just in front of the swing arm pivot.