It measures around 27cc atm I think, wrote it down, my jts head is something like 10cc. cylinder pressure is pretty good at 190psi on all but one (down maybe 2psi)

must have had the correct shave already so carry on :)
JTS head 10cc sounds like way too much taken off!

it might of been 17cc, I cannot remember but it was certainly one of two factors which blew my head gasket a while ago, running waaaaaaaay too lean was the other

mikuni has a good manual on their vm (round slide) series carbs I think you can download it free. The FZ1 and R1 came with round slide carburetors. The flat slide Mikunis are even better.

the fz1 carbs run a one liter engine 11,000 rpm producing 130 hp. I have an fz1 & love it.

They are very good carbs. Just bolt them on and run the engine a little with a wideband oxygen meter. That will give you a reasonable starting point for jetting. Dyno runs are important to get it right.

The jets are commonly available. I advise against drilling them as the bit does not leave a clean bore.

Jets are cheap enough I was just going to throw in 145 mains

There is little harm in changing jets as you can always go back to the old ones if need be. Each setup is different so check your jetting with the engine under load with a wideband oxygen meter