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RicardoJM
07-13-2010, 10:00 AM
I have two Aisan carbs and neither have ported vacuum. The date codes on the air horn are November 3, 1969 (9K3) and September 4, 1972 (2I4). Last fall I rebuilt the 1972 carb and have been very pleased with the results. I'd like to make the transistion to ported vacuum and am sending the carb base from the 1969 carb to Marks Offroad to have it drilled.

Will I run into issues if I take the ported vacuum base of the 1969 carb and use it on my 1972 carb? If the carb bases are compatible, I would make the swap. If they are not compatible, I will rebuild the 1969 carb. I've compared the 1969 carb base with photos of the 1972 base and have noticed two differences.

The first difference is the linkage on the 1969 base has the high speed valve stop lever (#1 in the photo). As I understand it, this lever is often removed as it is not needed.
http://www.risingsun4x4club.org/uploads/ricardojm/Carb/w_highspeed.jpg

The second difference is the number of passage holes on the top of the carb base. The 1969 has three and the 1972 has two. Both carbs have the passage holes indicated by the blue lines. The 1972 is missing the hole indicated by the red line.
http://www.risingsun4x4club.org/uploads/ricardojm/Carb/w_basepassage.jpg

As I only have the photos from my rebuild of the 1972 carb, it is possible that I am missing other differences. I also realize that with parts this old, it is possible the bases where changed out at some point in the past. Are there other differences between these two bases that I should know about?

MDH33
07-13-2010, 11:27 AM
I'll take a look at my carbs and see If I notice a difference. I have a '69 with ported vacuum on my 40, but I have a couple of other double barrels on the bench I can look at too.

I do recall from Dan's carb that there were some differences in the linkage configurations that might require a work-around.