how to identify carb size

[KARSTEN]

I am working on my still new to me '85 R80RT.having some issues with the bike not running smooth while cold,running with choke.the previous owner changed the cylinders out with the 1000cc.Now in order to order parts from Bing I will need to know if I am dealing with 32 or 40 mm carbs. are there any id markings on the carb or how can I look the needed info up?

[sumran]

There are numbers stamped on the carbs. On 40mm carbs it is on the angled part of the casting that runs between the seam of the dome and the top of the venturi. They can be difficult to spot if they are dirty.

The format of type/size/carb #. Mine are 94/40/109 and 94/40/110. The last number will be different for the left and right side.

[535is]

If they are the original carbs, they're 32mm. Even if they came with the 1000cc cylinders, they probably would be 32mm if they post-date 1978.

[AnnapolisAirhead]

If the PO changed just the cylinders they are likely 32mm. If the PO changed the heads as well, more likely to be 40mm.

The carb tops have either 4 screws (32mm) or 2 screws (40mm) from what I've had. Randy's method is the surest way to determine their identity (its on the webbing leading up to the dome top, I think on the choke side of the carb), besides Bing will need these numbers to provide the correct parts. Tougher for you, will be the size of the jets if the PO made mods.

:type

[88bmwJeff]

The carb tops have either 4 screws (32mm) or 2 screws (40mm) from what I've had.
:type

FYI, The 32mm carbs on my 88 R100 RT have only 2 screws on the top. So, that method is not a definitive way of determining. As mentioned earlier, the best way is to read the numbers stamped on the carb. The middle number, I believe, will tell you the size.

[jforgo]

94 numbers are always 40mm