Mikuni 28mm carbs

[davo63]

Hello folks, I've recently managed to buy a set of z1r 28mm carbs,I'm presently running 26s on my z900a4. Bike runs great on problems ,is there any benefit to changing over to the 28s ,midrange, acceleration etc ,or leave well along , thanks davie.

[zed1015]

The 28's are the sole reason for the Z1R's HP increase and performance over previous models so will provide an overall improvement when substituted for the 26's..

[davo63]

Thanks for advise, will change them over and see how it goes.

[DeadZedDave]

If you can let us know how you get in then it might prove interesting.
Kawasaki switched to 26mm carbs for the Z900 after using 28's since the Z1 was launched. The Z900 had fewer BHP (max) than the Z1.
At the same time the rear sprocket was reduced from 35 to 33 teeth (for UK bikes). Road tests at the time claimed stronger low speed and mid range power with the 26's. Kawasaki kept the 26's for the z1000A1 and A2 and only when the Z1R was launched did a return to 28's happen. The Z1R had more peak BHP. A number if road testers of the day argued that the A2 had better low / mid range even though peak BHP was less than the Z1R.
A decent set if 28's set up right will probably - all other things being equal - give you more power above maybe 6500RPM but below this number there will be less BHP and Torque compared to the 26's. Thats my own experience. It's worth asking yourself how you typically ride the bike ! If you spend a lot of time in the low- mid range then the 28's might not be as good as the 26's. If you ride around at higher RPM and regularly run in the 7000 - 9000 RPM range then the 28's should give a bit more top end.
All else being equal, you don't get anything for nothing !

[davo63]

Will let you know zedDave, won't be changing them over till the weather gets a bit warmer, still to see what pilot jets and main jets are in them. They were on a z1000a1 when I got them and the bike ran well, will keep you informed.

[Kev1R]

I had a Z1r since the 80's and acquired an A2 in 2013 - (and sold the Z1R in 2021). I still have the A2 but for a few years was able to make direct comparisons. I always felt the Z1r was more planted on the road and inspired more confidence but whether it was much faster in real road conditions is very debatable. Unless you are going to do track days I don't think on an average Sunday afternnon run you will notice much difference. I understand why you might try though - its always nice to have more power!