1978 Z1R -- came stock with 28mm carbs?

I don't have a 1978 factory shop manual (yet) for my 1978 Z1R and in researching this online, I keep finding info that says "the Z1R in 1978 did *not* have the 26mm carbs that came standard on the Kz1000 'A' bike -- the Z1R came stock with 28mm carbs, and the standard main jet was 107.5 and 15 pilot."


So I *do* have a 1978 Kz1000-A2 factory shop manual -- which says the regular A2 Kz1000 shipped stock with 102.5 main jets and 26mm carbs.

I need to order some carb parts and want to make sure I know which carbs I've got on my Z1R.


Is the 28mm carbs and 107.5 main jets information I'm seeing -- is it accurate for the stock 1978 Z1R?

And why can't I find a '28mm' stamp anywhere on my carbs?

Yes those are correct for the z1r,thes code numbers stamped on carb body should be in choke lever area I believe

wireman wrote: Yes those are correct for the z1r,thes code numbers stamped on carb body should be in choke lever area I believe

Okay good deal, clears up the confusion, thanks wireman, is it a '28' or a part number I should look for in the choke lever area?

Someplace on here is a list of what the carb I.D numbers are but Im not sure where it is :ohmy:
Ive got an 80 z1r in the barn I can check when it dries up down there,I don't remember if it still has 28s on it or not.

Stock D1 28mm carb jets (side-located pilot air screw)
Main 107.5R
Pilot 15
Needle jet 0-3 or 0-1
Jet needle SCN12 (clip grove number 3)
Service fuel level 4 ± 1mm

Good Fortune!

The measurement -- 26mm or 28mm -- is carb bore diameter on the engine side of carbs.

Easy method with carbs removed is to attempt inserting a 28mm round cardboard disc into the bore from the engine side.
If it goes in, it's a 28mm.
If it doesn't go in, it's a 26mm.

Good Fortune!

Hey Patton,Wheres the list of carb I.D numbers?
I thought there used to be one on here someplace anyway

www.kzrider.com/forum/3-carburetor/567082-mikuni-carb-id#567089

Good Fortune!

wireman wrote: Hey Patton,Wheres the list of carb I.D numbers?
I thought there used to be one on here someplace anyway

If it's here, it's well-hidden , perhaps deep under a non-descript barn in an undisclosed location southwest of Omaha. :lol:

Good Fortune!

Patton, I have posted some lists kzrider.com/forum/3-carburetor/530034-jet-size#530036 and a how to ID carbs for the (K)Z650s (vm22ss and vm24ss carbs)that you posted above.

I am working (have been for some time) on a list of the larger (28vmsc, vm26ss and vm28ss) carbs but it is not complete as of yet. At least it is not in a state that I want to post yet.

I will say that info I can find regarding the 78 Z1R carbs the ID that should be stamped on them below the choke handle (though it could be on the same flange on the other side of the carbs) is 1040 and would look something like this

104
0 (could be other numbers or letters after this)

They are were vm28ss carbs. Keep in mind I am not at this point willing to say that is the one and only correct ID stamp, but it is what I have found to date. I also have found info that indicates the numbers you posted about the jets and internals to be the same other than what I have found indicates they had pilot screws and not air screws?

gd4now wrote: Patton, I have posted some lists and a how to ID carbs for the (K)Z650s (vm22ss and vm24ss carbs) IDs. I am working on a list of the larger (28vmsc, vm26ss and vm28ss) carbs but it is not complete as of yet. At least it is not in a state that I want to post yet.

I will say that info I can find regarding the 78 Z1R carbs the ID that should be stamped on them below the choke handle (though it could be on the same flange on the other side of the carbs) is 1040 and would look something like this

104
0 (could be other numbers or letters after this)

and yes they are were vm28ss carbs. Keep in mind I am not at this point willing to say that is the one and only correct ID stamp, but it is what I have found to date. I also have found info that indicates the numbers you posted about the jets and internals to be the same other than what I have found indicates they had pilot screws and not air screws?

Thanks, gd4now, for the list and also for the posts in previous threads that include pictures of the many various Mikuni manual slide carb varieties, with notations regarding the physical differences in appearance, and how to identify them one from the other.

Am thinking the currently sought-after list would be a similar chart showing the particular tiny i.d. numbers stamped on each variety of larger Mikuni carbs. Have been unable to locate such list of i.d. numbers associated with the respective carbs, on KZrider or elsewhere. Thanks for the on-going efforts in this regard.

Using the term "air screw" or "pilot air screw" or "pilot adjustment air screw" or other variant containing the word "air" is to emphasize that the pilot mixture on carbs having a side-located pilot adjustment screw is leaned or enriched by adding or reducing the volume of air introduced via the screw position.

This is in contrast to where the term "mixture screw" or "pilot mixture screw" or "pilot adjustment mixture screw" or other variant containing the word "mixture" is used to emphasize that the pilot mixture on carbs having a bottom-located pilot adjustment screw is leaned or enriched by adding or reducing the volume of mixture introduced via the screw position.

The terminology is just an effort to avoid confusion between the two types of pilot adjustment screws, where the side-located screw is an air screw, and the bottom located screw is a mixture screw.





Good Fortune!

Patton wrote:

wireman wrote: Hey Patton,Wheres the list of carb I.D numbers?
I thought there used to be one on here someplace anyway

If it's here, it's well-hidden , perhaps deep under a non-descript barn in an undisclosed location southwest of Omaha. :lol:

Good Fortune!

That would take hours of climbing over stuff with a flashlight! :woohoo: