I disagree, 180b are similar but different, I have a pair of these same square top carbs [pictured] on my 1200 GX induction setup. the linkages are totally different between 180b and 1200. Even down to the linkage that connect the choke assembly to the throttle shaft linkage [to partially open the butterfly when the choke is in operation].

benny sorry i ment they are the same in regards to how much they flow as they are both 38mm
and i spose you could say these arent genuine gx "carbs" as they where found on other models but so where the dome tops which where also on early roadsters and the 1600's the only specific gx item is the manifold. nearly everything else can be found on other models

38 mm
* HJB38W: Roadster R engine (SPL311-1600)
* HJB38W-3: Roadster with G engine, also 1968 R engine)
* HJE38W: B110
* HJL38W6: 510 L16 & L18

46 mm
* HJG46W: Roadster U20 (SRL311-2000)
* 240Z, 260Z

And there are more...including the 38mm 610 carbs.


The emission controls are not the kind that hurt performance. Just some simple stuff like vapor recovery. They didn't meet emission control specs for USA.

manifold comparo

The B110 and B210 A12 manifolds are almost identical, they might even be the same casting. The B210 ones have a couple extra vacuum bosses drilled out. One I think is for the power brakes.

From what I have seen over the years I came to believe that Hitachi did a running change on the carbs in 1973 where the round top carbs got square tops without changing anything else that I could see. These were still secured to the standard 1200 GX manifold.
I remember seeing these carbs in a few photos in the last couple of years.

The next development was to change the main body of the carb for the polution functions. The carb linkages are unique to the A series engines, including the throttle shafts so carbs from any non A series engine would need to be rebuilt with the correct GX type throttle shafts to work on this manifold.
What do you think the chances of that are.

I'd say that someone pissed before geting it out of his pants with this thread.

My apoligys Sidedraught. Clearly as dodgeman suggested I did spent too much time scratching my arse instead of my head. (they may be the same thing, you have seen the photo's) But the question still stands. Are square top carbs, albeit non pollution, still considered 'GX'?

if you want to be technical they did not come off a gx 1200 so i spose no they arent but they are basicly the same thing so why not call them gx carbs?

If Dodgeman is right about Hitachi changing over to square tops in mid 73, there would still be a possibility that they may be off a 1200 GX.

does it matter if the carbs are off a 1200 gx? its the same thing as stated by dman if your really fanatical about having round tops go find your self a pair of early round tops off a roadster or 1600 change over the jets and linkages there you have your self a "genuine" set of gx carbs no one will pick the difference. but then you cant buy rebuild kits for the round tops so i think i would rather have square tops

whats the function of the middle bit that joins between the 2 side bits of the manifold?