EFI for 1980 KZ750H1 LTD

Hmmm, remember you can always go too large! :laugh:

You might want to ask Dave Sloan, he has the 1100 TB's on his 650 (810?). I remember him writing somewhere that when he is cruising his butterfly valves are hardly opened. With even bigger TB's this will get worse.

This means it is more difficult to tune the mixture, because there is a big difference in Manifold Air Pressure (MAP), between cruising and when you have the throttle wide open.

The standard 750's have 34mm CV carbs. A CV carb has a lot of obstructions in the airflow. There is the butterflyvalve and you also have the round slide with the needle attached to it.
A normal injection TB only has a butterflyvalve obstructing airflow.
So if you want to compare the sizes of carbs and TB's you have to take this into account.

Most modern sportsbikes have 4 valves per cylinder and have very high revlimits, this means it is possible to suck more air in. So you need a relatively large TB to let all the air through, and make a lot of HP.

The old Kawasaki 750's have only 2 valves per cylinder and a relatively low revlimit, so there is a limit to the amount of air they can suck in.

If you make the TB's bigger, the airvelocity in the TB's will be lower. This has an effect on the torque and HP you will make.

The 750turbo TB's have a funny shape (they go from 34 to 29 mm). On a turbo this doesn't really matter, because the mixture will be pushed though it.
A lot of people think the turbo TB's are a bit too small for a 650 or a 750. The 1100 TB's are maybe a tiny bit too large, but an easy choice, because they will fit without too much trouble.

I think a 32mm TB from a modern bike would be a really good option, but you will have to adapt the spacing...