Today I was finally able to leak test both tanks. I had struggled with too large of balloons, leaky hose on my bike tire pump, and generally not having time to do it. Today everything finally worked out and I was able to do the test.
I bought the test kit from Van's and it worked well. First the fuel pick up tube was capped with the blue fitting. Then a balloon is placed over the vent line. Lastly, a fitting is screwed into the drain sump and connected to a bike tire pump. I then pumped up the pressure in the tank until the balloon inflated which Van's says is about 1 psi. The balloon acts as a relief valve so the tank isn't over pressurized which could damage it as it isn't built to hold pressure.
Once the balloon is inflated, soapy water is sprayed on all joints, fittings, rivet heads, and generally anywhere a leak could occur. On my left tank I found that the balloon was leaking around the fitting it was slid over. I used some copper wire strands that when tightened pinched the balloon in the threads of the fitting and slowed the leak, but didn't stop it. I also found two of the screws for the fuel level sender mounting plate were leaking. I snugged up the screws a little bit and both leaks stopped.
The right tank test was uneventful and no leaks were found. It was still holding air pressure the next morning after the test. This process turned out to be easy and it feels good to have leak-free tanks.
