Fuel tank venting

[Kurlon]

Slowly making progress cleaning and prepping the tank I got from Kayla, and learning I don't have the patience for proper paint prep. :D I also learned Meal Rescue / Evapo Rust are killer for cleaning rust out of tanks, that thing is SPOTLESS inside now without any good metal loss for acid etching. The tank is sitting in some in that pic, getting the last of the rust out from the bottom where it was hidden by the rubbers.

So, anyways, I've got one question on the tank... Under the cap are 5 holes. 3 are for the cap retaining bolts, check. One is for the overflow drain and goes to a bung on the bottom of the tank, check. That leaves one that I assume is the tank vent. I can't blow air through it with my air compressor. Should I be able to or does it have some sort of check valve assembly?

[Kayla850]

The fifth hole is for a tiny M6 x 10 (possibly 8mm) bolt that holds the standard filler cap assembly in place underneath the actual cap once it's closed. I suppose it's a bit of extra security. The tank breather/overflow are one and the same.

[Evilchicken0]

I thought the tank vented through the fuel cap, when you take it apart you'll find a labberinth seal. That why the tanks sing like a siren when you put the bike away

[Kurlon]

With the keyless aftermarket cap setup, the vent path is the bung on the bottom of the tank, up the tube, under the cap assembly. From there it has to go through the dual spring/ballbearing check assembly under the threaded cap and into the tank opening.

As long as that check assembly works, and the o-ring keeps the cap from screwing down too far, I should be good to go. I already filed down the legs on the outer cap frame so it'd seat and get a proper seal on the main tank opening so leaking shouldn't be a problem when inverted.

Now I just need to figure out a good lazy way of sanding in that recess other than by hand and I can get to painting.

[rockTJ]

I also learned Meal Rescue / Evapo Rust are killer for cleaning rust out of tanks, that thing is SPOTLESS inside now without any good metal loss for acid etching. The tank is sitting in some in that pic, getting the last of the rust out from the bottom where it was hidden by the rubbers.

Does anyone know of an equivalent product to these in the UK? I have 2 FZR250RR 3LN tanks that need the rust getting rid off

Chris

[Evilchicken0]

Citric Acid ... or you can buy the stuff advertised in classic bike mag. Or drop the tank round and use mine

[Kurlon]

Citric Acid, Vinegar, CLR, those are all acid based. They'll work, but they also attack the metal, just at a slower rate. Metal Rescue and Evapo Rust use chelation to go after the iron oxide only. Not that big a difference if you've got good metal and light surface rust, you won't have the acid in there long enough to do any real damage. If you're cleaning out a nasty rust job, the acid will be in there longer giving it more time to eat good metal too.

Quick digging says Metal Rescue has a UK vendor, but they don't list who it is. Evapo Rust shows http://www.evaporust.com/country/uk.html as their distributor across the pond. If you go with these, damn the directions you can cut it 1:1 with water to make it go further. I used 3 gal and then added enough water to fill my tank, took about 5 days to get it spotless.

[Kurlon]

I didn't end up taking all the bondo off, and got sick of sanding so it's ugly in spots. The end goal was to make sure the tank is sealed to prevent rust, cosmetics are secondary... Put down a solid primer base followed by high temp gloss black as per the instructions for both. Only got a couple runs to sort, a wet sand will sort that. What I can't explain are the random blue patches in the paint? No idea what's going on there, hopefully the final black layer will cover them before I lay down the clear coat?

[Evilchicken0]

I use a Black and Decker Mouse palm sander they're really good. The blue is probably a reaction to the existing paint below maybe you need a coat of clear primer.
Finish as ever is dependant on the prep below.

[Kurlon]

There was no existing paint below, I took it down to metal then covered in Rustoleum primer before painting.