Why does my Hs 85 leak a lot right after I fill the tank?

Almost all fuel tank have a cartridge for absorbing the fume of the gassoline and not for over flow
For your case it seems you have a leaking fuel pump gasket so when you fill up it might come out from it

There are two hoses running from the filler neck. Either of them could be leaking from the top. There is also a seal on the top of the tank where the fuel pump is that can leak. If your car leaks the whole time you are putting fuel in, I would suspect the hoses. If it only leaks when you get it full, then check the seal on the top of the tank. The top of the tank can be seen without dropping the tank. Remove your back seat and you will see a cover over the fuel pump. Remove that cover and you can see the top of the tank.

Any hardware stores where plumbing supply is sold including lowes and home depot sell toilet seal kits including toilet to tank seals as well as toilet rebuild kits. Ask for a toilet to tank seal and washers for the bolts which might come with the large seal(check)
1. Close toilet water valve
2. Drain tank or sop with a towel and squeeze into tub until toilet is empty or bail water out with a cup.
3. Remove two tank bolts
4. clean area where old seals were
5. put tank seal on bowl and set tank lining it on top of seal.
6. Install tank bolts with new seals and tighten evenly
7. Don't over tighten or tank will crack. You probably can tighten until tank and toilet touch evenly on both sides.
8. Fill and check for leaks.

It can be. Anytime fuel is leaking, there is potential danger. I suspect the seal they're talking about is the one right at the top of the tank. Unfortunately you have to remove the gas tank to repair it. Quite likely this faulty seal will cause the engine light to come on also as it will cause a leak in the evaporative system.

under so circumstance should it leak out. Either the filler neck is leaking or the seal for the fuel pump. You will need to lower the tank to check it out.

Yes. You will have to remove your tank from the bowl to replace the defective fill stack(the tube thing your flapper is attached to) it is not as hard as it seems.First remove water supply tube.Then remove the through the tank bolts. should be two of them. Lift off and turn tank upside down. remove spud gasket. Unscrew old stack. You should be able to get a universal kit to work with your tank and should come with all new parts including new flapper and spud gasket. You will need new through the tank bolts and note the sequence of assembly to get water tight seal on tank. Hope this helps

your main seals are probably bad advise to buy new

had a similar problem. it was the filler pipe. it only got worst and worst. I got one in excellent condition from a junk yard and it cost half what I was quoted.

Probably a main tub seal, big job!