Thanks for your advices.
Though the saw is totally new, and you maybe will think that I am lunatic, but the normal start (original) is however displeasing .
You know it is a small saw, i mean 1500 w, and there is no belt, only the blade attached to the motor with 2 internal sprockets in way to shift the axis on the motor's side.
So very simple.
I really think there is no mechanical problem, and i tried the motor without even the blade, all is normal.
Maybe the problem is in my head
but I don't like the motors starting brutally.
I think i will contacvt Ryobi and ask for buying the soft-start that equips on their bigger saws.
But you know that all the spares parts are always so expensives, (if you buy a car only in spares part, you will pay ten times its global sell price)this is why I hoped to make a soft start by myself, because i tried, and a simple light gradator makes exactly what I want.
But it works manually, and I would like to make it automatic.
Anyway thanks for your interventions, i will wait more, and maybe someone (electronician) will help me, because, between us.....
how could I cut the six feet long fishes that I fish everyday if my saw doesnt work as I wish ???