Use as large a line as will fit thru hole and still be snug on carb fitting. After a while it will compress where it enters tank and may still leak a little though.

Thanks wprice, I just didn't seem to have a good fit for a particular hole. I actually went back to the expand a hose first by pressing a small male/male fitting into the loose fitted hose to expand it. That worked; more or less.

On my Husqvarna trimmer, they use a "fuel tank bushing" to seal the fuel line hoses. There may be something like that available for your Yardman trimmer. Here's a link from ebay with a picture to show you what it looks like: http://www.ebay.com/itm/Husqvarna-Equipment-OEM-Gas-Fuel-Tank-Bushing-503735801-/140535526764

You should be able to go to one of the small engine parts sites like jackssmallengines or ereplacementparts and look at their parts catalog for your trimmer and see what's available.

BTW, the price of the bushings on ebay is about 3 times what I paid for mine.

I ran into the same problem on an old chain saw. Get the correct ID line size which has a larger OD than the hole in the tank, cut the end at an acute angle and slide it into the hole, use a pair of doctor pliers (hemostat) to pull it through while stretching on it from the outside. The line grys smaller as you stretched and when you get it long enough into the tank to pull it through the filler hole let it go and it will swell back to original size to form a "seal" in the hole. Cut the acute angle off, install the filter and attach the other end to the carb.

Hope this helps, it's early and I am still asleep.

You need a double barb union fitting, Poulan part number 530-023877 or equivalent.

http://goosegear.com/120858-fuel-line-fitting-poulan-530023877?gclid=CKOH0uDLs8UCFdYUHwodLYMA9A

If the link doesn't work, Google 530-023877.

You fit a length of tubing on each end of the barb. One goes to the carb, the other goes into the tank. Push it through until the barb enters the tank. It will expand the hose enough to make a tight seal. Be sure you leave tubing to the tank long enough to fish out the end so you can attach the pick-up filter.

What i do is take the current hole and get the next size up that is too big to slide in the hole. Take a drill bit 3/32 smaller than the tube you are going to use and at a high speed drill out the hole feeding in the bit slowly but spinning fast so that wall is smooth.

Take the hose and cut one end at a 45degree angle and push it in while twisting it until you have lenght in the tank enough to grab with pliers and pull it through.

The hose needs to be in there very snug because over time, it will shrink and leak if not.