I've got my carbs off for cleaning, and notice the main jets are 130 for cylinders 1 & 4 and 125 for 2 & 3.

Is there any good reason for that?

It's a USA 2006 model, not California. Pilot jet sizes are 38 throughout.

That is common for Kawasakis.
Zzr1100 had the same.
They know more about engines than I do so I just accept it must be right.

Thanks, Bob. I've since read that on an inline four, cylinders 2 & 3 run hotter than 1 & 4. A bit like your soup is hotter in the middle of the bowl.

That totally makes sense, but I have seen conflicting views about whether 2 & 3 therefore need more fuel or less. Anyway, I'm going to downsize all jets and try a home-made version of Steve's 2-minute mod. I wanted to buy the kit, but he told me he doesn't ship to the UK.

As for the #38 pilot jets, all I can see on the forum is #35. A look at the spark plugs suggests the bike is running rich.

I don't think that's how it came OEM.

I've been inside a couple dozen sets of ZG1000 carbs including CA models.

They always had the same main jet sizes for all 4, 130 for CA and 125 for 49 staters.

. . . 130 for CA and 125 for 49 staters.

And that's what it says in the manual. Canadian ones got 125's also.