Is this another website or is it your own?
If you have already made a wheel which gives you a succesrate on 1/50, then it should be pretty easy to change that to 1/1.
If this chance was made with PHP then try and search for this statement "rand". This statement gives you a random number between two numbers inside it.
Now it is probably written like this: rand(1,50) and you will have to change that to rand(1,1)
Hope this helps.