We run a 38mm in Stock Moto so 39 will be fine, save your money.
I have told you what you need to do to get it to run, we ran pilots in the 40’s when we ran a restricted Jr125.
It should not idle, the motor fuel requirements are much different then a bike.
Jets are cheap, put them in and you will be close.
New jets get clogged just as old ones do, run a filter.
Trust me go run it and report back, I gave you a fat set up but will “rip” at all rpms.
edit: 32:1 is what we always run