first of all let me say im new to small engine repair but i took this on as a hobby as i find lots of small engines on my ventures but ive come across an issue no-one yet seems to be able to answer..everyone is the briggs and stratton engines, a toro lawnmower, Tecumseh all the briggs and stratton..btu anyways i fix them and they do work all of them but they will onyl start when the filter is sprayed with carb cleaner..every one of them...why that is i dont know...ive dismantled them cleaned the carberator out evem the filter , and in one case my moms lawnmower jsut replaced the carberator and replaced the filter and yet still it has that problem tha tit will only start when sprayed with carb cleaner in the filter...you can pull it 15 times and prime it 15 times and it wont start but once i spray carb cleaner into the filter it starts right up and mows great..i can mow the whole lawn no problem...but once it sits idle for an hr its the same problem all over again..its the same with every briggs and stratton motor ive come across..i have 4 lawnmowers right now at my dads that 3 of them are "repaired" but has this issue only ..i would like to know why this is and how i can fix it as i can say they are fixed to perfect working order...any help out here for this? and if it helps these carberators dont have the adjustment screws if that helps.