Z1OwnersClub GB

What difference if any would fitting Z1r 28mm carbs to my 903 engine? Currently has 26mm I think certainly not the early carbs.

Jon , You said 903cc engine ! Is it a Z1 or Z900 ? If a Z900 would suggest leaving the 26mm but if a Z1 the newer 28mm will be OK if you change the pilot jets / mains jets to suit . I ran my Z1B for years with a set from a Z1000 MK2 and no problems . I had to blank off vacuum fuel tap feed and they fitted straight on with standard air filter also !

Jon, bung 'em on "suck & see"..... They may not need much adjusting, at all

I've used these Z1R 28 mm before on Z1 and Z900's. They are "high tops" so they look like the 26mm Z900, would be hard to pick the difference visually. Mainly though, they fit and they perform.
RegardZ.

If you want to knit pick they will give slightly better top end and slightly worse midrange response - air velocity when opening up will be lower on the 28s. I would doubt you will notice for normal riding, stick them on and do a comparison with the 26s and see which you prefer.