It took a while, I am happy to report that the 16T front sproket is installed, along with a new chain, new rear sprocket (stock spec 39T), and a new cush drive. I had my favourite repair shop to do it. It was just too much for me to do it myshelf.
I have never heard of a cush drive, found out that it is a rubber dampering piece that keeps the rear wheel running smooth during power delivery. The new one is an updated version, looks a lot more skookum than the original.
Just put on 75km of city and highway riding, I am Impressed! The ZR750 runs like a dream. There are 2 observations:
First, the new running gear system- the power response is instant, smooth, no jerky motions, no delay. The bike runs quieter. I never knew chain drive could be this smooth. It is even smoother than all the shaft driven bikes I had owned.
Secondly, 16T sprocket ratio - fits my riding style even more. I now ride in between 2 and 3 gear in most city situation. The 1st gear is for taking off from a dead stop. The 4th is like the high gear, and the 5th is like an overdrive. In 5th, travelling at 120kmph on the highway is comfortable, the engine does not sound like it is rushing or labouring. Kick it down to 4th to pass, the bike just accelerate thru the power band. I didn't notice any reduction in performance at city speed.
Overall, I highly recommend going to the 16T front sprocket and installing the updated cush drive.
Thank you for all your inputs and assistance.
Kenny