Help identifying strange VM26 markings.

[Agemax]

I am restoring a set of VM26SS carbs from a USA imported GS1000, for some strange reason they have been bored out and had a stainless steel sleeve fitted. The ID of the sleeve is exactly 26mm. All 4 carbs have this sleeve so it is a deliberate modification, rather than a repair job on 1 carb.
You can clearly see the sleeve in the attached picture. I cant think of a reason why this has been done, and i have never seen it on any other set of VM's i have restored in the past.

A possible clue is that apart from the usual carb ID number stamped on the flange (49010), on the other side of the flange there is 7 Z1 stamped on it.

Has anyone seen this before, is it a mod that is carried out by someone in the USA?
It clearly isn't going to be an issue with the carb operation, i am merely intrigued to find out the reasoning behind it.

TIA

 

[Big T]

I can't say that I've seen that modification before.
But, there is a guy who would make your carbs flow more air - Maxi Bore was his process

 

[tatu]

Could it be somebody sleeved down some 28s' for some reason? Not really GS original fitment?
I had that set of Kawasaki rack if you remember that were identical to GS kind except the air screw adjustment was absent.

 

[Agemax]

Could it be somebody sleeved down some 28s' for some reason? Not really GS original fitment?
I had that set of Kawasaki rack if you remember that were identical to GS kind except the air screw adjustment was absent.

The ID number on the carbs suggest they are Suzuki original VM26's.The bore at the venturi measures 26mm so they had to be 26's to begin with. They have both air and fuel pilot screws.

 

[zed1015]

A pic and measurement of the carb mouth would help.
If they have been bored out to 28 or 30mm in the past then the mouth will also be 28 or 30mm and the sleeve has been used on the engine side to return them to stock ( although stock 26's are actually closer to 27mm at the boot side).
If the mouth appears stock then the sleeves are there to repair damage or some other unknown reason to one or more of the carbs and all have been done to maintain matching flow between them all.

 

[Agemax]

A pic and measurement of the carb mouth would help.
If they have been bored out to 28 or 30mm in the past then the mouth will also be 28 or 30mm and the sleeve has been used on the engine side to return them to stock ( although stock 26's are actually closer to 27mm at the boot side).
If the mouth appears stock then the sleeves are there to repair damage or some other unknown reason to one or more of the carbs and all have been done to maintain matching flow between them all.

As i said, they measure 26mm, so they haven't been bored out larger.
It makes sense that have have all been sleeved so they all match but there is no obvious reason why. I think the clue is in the 7 Z1 stamped on them, i have never seen this before.

 

[zed1015]

As i said, they measure 26mm, so they haven't been bored out larger.
It makes sense that have have all been sleeved so they all match but there is no obvious reason why. I think the clue is in the 7 Z1 stamped on them, i have never seen this before.

The 7 Z1 was most likely put there by the person who sleeved the carbs.
No kawasaki ever had VM26 or 28mm carbs with both fuel and air screw as stock so they are original Suzuki fitment, either GS750, 850 or 1000.
If they are stock on the airbox side then the sleeve is either to repair a damaged carb and the others were done to match or they have been altered for another reason.
If it wasn't to repair damage, all the sleeves would do is maintain a slightly higher velocitiy in the carb body as the originals tapered out to the boot side to almost 27mm.
There is another possibility that the rack has been made up of mismatched bodies of which they have used two or more with the port in the bore wall for a vacuum tap and have done this to block them off but if this was the case there will be additional mods , drillings and blanking plugs to make those bodies suitable for their new position.

 

[Agemax]

I know they are Suzuki carbs because of the ID numbers. They are all otherwise untouched and unmodified. The sleeve does not go far enough to interfere with the vacuum port in #3 carb, they are all the same length and go in as far as the original "step" in the throat where it changes from 26 to 27(ish)mm.
Because its a USA import bike i was wondering if any of the USA members had ever come across the 7 Z1 id stamp or a clue as to who, or what company it may have been.

 

[rphillips]

I'm no mechanist, but that seems like a lot of trouble to repair a carb that should be readily available & easily replaced. Those carbs were used on several bikes for several yrs...But looks like a nice job.