Mikuni 28mm?????

I pick these up at a swap meet. At first I though they are for a 78 Z1R. But they have a dual feed. When I got home I measured them, 27mm.
My questions are:
1. Are they 28s?
2. What are they off of?

Guessing 26mm used on '76KZ900.

Excellent, user-friendly carbs, before the stringent environmental regulations came along.

Should perform well on a 1977 KZ1000.

Good Fortune!

Hard to tell from the pics can only see an air screw - not sure if there are pilot screws on the bottom or not. If they have both they are vm26ss carbs from a Suzuki as they had both types of adjustment screws, while the 26s used on the Kawasaki's did not have both.

There were some 28s used on the Kaw's that had double fuel inlets with the large idle adjustment screw on top like yours have.

There should be some IDs stamped on the carbs either on the flange under the choke lever or on the same flange on the outside of #4 carb. They may help to Id them.

When you measure them you need to do so where the slide meets the carb throat and not at the intake bell or exit bell.

This is ID stamp. I never knew these carbs had them. Thanks. Is there a chart with these ID stamps on them?

ID stamp.

VM26SS indeed, they are actually 27mm bore like you measured

very nice and well made carbs,

OK I have not see one with a Z as the first character like that, but then I have not see all the carbs there are.

It is my understanding that all of the 12xx ID carbs are vm28ss carbs other than those with a 1202 ID which are vm26ss carbs.

Having said all of that I do not mean to imply I know all there is to know about the IDs on the vm26ss and vm28ss carbs. I have been trying to build a table or data set regarding the stamped IDs on them. Though I do have several different IDs currently, I do not have enough to post a table as of yet. I do have one and have posted it for the vm24ss and vm22ss carbs used on the (K)Z650s.

I suggest you measure them, where the slide meets the carb throat. Can do so with several different methods. Use a socket that is less than 28mm od but more than 26mm od. Pull up or remove the slide and see if it fits. If it fits it is a 28 if not it is a 26. You could also use a set of calipers or cut plastic or cardboard circles of the appropriate size and see if they fit.

VM26ss do not have any taper in the bore, if they are 27mm id then they are the 26ss.

OK. Thanks
I was hoping 28mm for my Z1R.
Would be nice if we had a data base of the ID numbers on Mikunis. These could be for Suzuki too, I got these from a drag racer.

I beg to differ - it is my understanding that all of the vm Mikuni carbs do have a taper on the bore - otherwise there would be no venturi effect and no real pressure difference that allows for the fuel to be pushed or pulled up into the carb.

I am not saying they are not vm26ss carbs, but I would measure them to see just what size they are. I for one would like to know to add this ID to my data set.

no problem GD, and I have no way to demonstrate that i am more knowledgeable than you. just about 35 years +/- working on bikes, road race tunning and plenty of carb racks everywhere....

so do i need to take a photo of a VM26SS straight bore for you to believe me or you'll take my word for it?



most performance oriented carbs (and the VM26SS were quite performance oriented, just not as much as 28 smoothbore VMs) have straight bores and a venturi created upon air ENTERING the carb). the more touring oriented carbs (like the VM's of KZ650s, the ones with the ribs), had the venturi enlarge also on the engine side for even more slow speed response/less top end flow.

Turbo - first I do not know if you do or do not have more knowledge than I do, but I think it is rather presumptuous on your part to assume that you do. I have also been wrenching and racing bikes for just a little longer than you have been - about 45 years and like you I too have been through many different carbs in that time. So as you say I can not demonstrate to you that I have more knowledge than you do.

And I will say there is indeed a difference in the diameter of the intake bell opening and the throat where the slide meets it. It is this narrowing that creates the venturi effect (pressure differential) that allows fuel to be pulled up into the carb throat.

I have attached a pic of a set of vm26ss carbs - you tell me is the opening at the intake bell larger or the same size as throat is where the slide meets it.