There are actually quite a few environmentally friendly rust removers on the market so it's really a matter of experimentation to see what works. I found this product called Evapo-Rust, that says it has a built-in rust inhibitor like Rust Rescue. They all run about $25 a gallon, and they all have convincing demonstrations on their website. I picked Evapo-Rust only because they had free shipping.
After multiple attempts with Rust Rescue I was pinning my hopes on this product. I rinsed out the tank with hot water and Purple-Power to get rid of the WD40 that I had sprayed in the tank to prevent any more rust occurring; there certainly wasn't any more rust than ten days ago, so I think I helped myself there. Then I screwed back on the old petcock and filled the tank completely with Evapo-Rust. With the heating pad on top to ensure that the temperature stayed above 60F, and the tank wrapped in multiple layers of towels for insulation, I left it to do it's magic for 24 hours. The documentation says 4 hours is sufficient, but I wasn't going to take any chances. As it happens, I ended up leaving it in for 48 hours, and swapping the heating pad from on top to under the tank halfway through to ensure adequate temperature all round.
Compared to Rust Rescue the level of iron oxide removal with Evapo-Rust was quite impressive, but more importantly the occurrence of flash rusting after the product has been removed DID NOT happen. This I was most pleased about. Just in case, I dried the tank completely with the heat gun, to make sure there was no residue water to start rusting the tank as before.
I purchased from Dime City Cycles this lovely chrome petcock to replace the OEM one. Reasons for doing this were not just cosmetic. The OEM petcock requires a vacuum line from the carbs to open the fuel line; with the new Mikuni's this option wasn't available, at least not easily. So I'm going old school, with a petcock that you have to open and close manually.
The petcock mounting bracket required new holes drilled to match my tank, and the tank opening required enlarging slightly with the Dremel to accept the round petcock fuel filter. After this was completed I vacuumed the area with the shop vac and a small nozzle, and then rinsed the tank out twice with gas to capture as much of the metal dust as possible.
With a few wraps of PTFE tape I tightened the petcock onto the bracket and then mounted that to the tank. Note: The two rubber washers are from Lowes and not entirely the right solution. I need a hard rubber washer rather than these soft washers which deform considerably when tightened down. For the time being they will work and hopefully not degrade too fast due to contact with gas. I've ordered the right washers from Partzilla.
Running from the new petcock I used some 5/8" clear fuel line to connect the new inline fuel filter, then some 1/4" line to run to a fuel line quick connect/disconnect: I'm going to be messing with the carbs a lot so wanted to eliminate the hassles of constantly having excess gas spill out of the fuel lines when removing the tank. From this more 1/4" line to a T-connector to split the fuel line to the individual carbs. Everything has been clamped with fuel clamps, but even without them the barbs on the connections holds things pretty securely.
It really was a lovely sight when I opened the petcock and saw the fuel trickle through the clears lines and into the carbs. No leaks too. Brilliant!
Current hours on build: 189.0