Super Tigre 40 is one of my favorite engines among all my collection. (The previous italian version)
The unique problem with it, is that it is very misunderstood.
At first flights your low speed needle valve should be somewhat open; this normally will tend to stop the engine from running when you open suddenly the throttle.
You have to live with this issue maintaining the engine a bit open with your TX throttle trim. (Just for a short time)
After one gallon or so you may start leaning the low speed needle valve until the engine transitions from low to high with out any problem, after several more flight this task will have to be done again and from there you will never have to touch the needles again.

I hope this can be of help.

Best regards.

Alfred.