I think if you have a varnished carb, SF will do nothing for you. I have restored what I thought to be beyond use equipment, especially 2 cycle with it, but none of the "been sitting 2 years" stuff. Worked great for what I use it for, but I used a lot more than the recommendations on the can, initially. Never did/had to do the "decarb" procedure you will find on here in the archives section.