Agree about stock size on stock rims.
Front 3.25-19
Rear 4.0- 18
Rear look a little bit slim compared with 120/90-18 that becomes very flat when worn which will give really bad handling when leaning the bike just a little. Like an angry snake.
My 4.0 need to be replaced and did not got shorter life compared with wider tire. Longer use with better handling.
Bike has around 100whp.
The tires lived short with less displacement and 80whp too. My hobby is test runs of latest carb tuning which means a lot of wot
When OK time for changing carbs or exhaust and redo it.
I like Heidenau K36 rear and K44 front. Old style look, modern rubber. Perfect for a CB750.
My last rear in the 80's was Metzeler ME99 130/80-18.
I loved those tires. Back then as wide as possible. 3.50 front needed some force to put the wheel on.