Two unrelated questions

[Larry D]

I have an 81 GS750L.
I'm getting ready to por-15 the tank.

1. Is there a preferred method of getting the last two cupfulls of fuel and the rust flakes out before beginning?

The petcock I removed was surprisingly clean. Maybe it's still good. It's disconnected and sitting on my workbench.

2. Is there a way test it while it's not connected to anything?

I searched and searched and couldn't find anything on these issues.
Thanks Everyone.

[argonsagas]

If you have the petcock removed there should be no problem in removing the last bit of fuel. Just tip the tank, drain it, then safely dispose of the gasoline.


Cleaning is best done with hot, soapy, water and a lengthy rinse afterwards..

That said, a garden hose at full flow will do the job. Move the hose tip around to be sure you get water everywhere as you need that to dislodge small rust particles.

Invert and drain the junk several times, then invert the tank and spray the hose from underneath to get out the last bits.

Leave it to dry completely before going farther.

[argonsagas]

Sorry for the second post.

The petcock can be disassembled, cleaned, and then re-used. Gaskets are available from the dealer.

[Nessism]

Sealing the tank properly requires you to prepare the metal before hand. The Por15 tank sealing kit included three products; gas tank varnish remover, tank phosphate wash to remove the rust and prep the metal, gas tank sealer paint. If you don’t have varnish in the tank it might be okay to skip that step but the phosphate step is critical. My suggestion is to keep the phosphate solution in the tank until all the rust is gone or converted (may take a couple of days). If a chalky residue is left on the tank, follow the phosphate with some alcohol and a bag of aquarium rocks to scrub down the surface of the tank. Dry completely followed by the sealer. My opinion again, but the small can of Por15 sealer is pretty skimpy for a large GS tank – I recommend two cans to make sure all the surfaces are coated. It’s only an extra $10 or so but will provide assurance the entire tank is coated.

Hope this helps and good luck.

[Larry D]

Thanks for the responses.
The point about the petcock is...it may be good, I don't know. Is there a method of testing it while it's not connected to the fuel system?? It's just sitting on the table waiting to be reinstalled and I'd like to test it.

[bwringer]

Thanks for the responses.
The point about the petcock is...it may be good, I don't know. Is there a method of testing it while it's not connected to the fuel system?? It's just sitting on the table waiting to be reinstalled and I'd like to test it.

Connect a clean hose to the vacuum port (the smaller one) and suck on it.

If you can hear the clicking of the valve, that's good. If there's no click, or you can suck air through there, that's bad.

Next, hook up a MityVac to the vacuum line, pump it up until the valve operates and see if the diaphragm holds pressure.

You can then hook up a clean hose to the fuel port (the larger one) and suck on it see if it operates as expected.

With no vacuum applied to the vacuum port and the handle in the "ON" position, you should get no flow. Apply vacuum to the vac port and you should get flow.

With the handle in "RES", it should operate the same.

With the handle in "PRI" (prime) you should get flow through the fuel line with or without vacuum.

None of these tests tell you whether the thing will actually leak gas from dried-out rubber parts, and the vacuum tests can miss a pinhole leak in the vacuum diaphragm. But you'll be in the ballpark.

Don't try to rebuild it. Rebuilding old petcocks is iffy -- a 50/50 chance at best. It's a far better investment to just get a new one and forget about any problems for another 20 years.

If you have any doubt whatsoever, sell some plasma or mug a few tourists, spend the lousy $50 and replace it with a new one from Suzuki. As I've said before, it controls the flow of an extremely flammable substance mere inches from your crotch, and it can cause massive engine damage if it leaks and fills the crankcase with gas. And burn down your house. You do NOT want this thing to fail or leak.

If it sorta looks new-ish and uncorroded, operates smoothly, and passes the vacuum tests, I'd give it a try once the bike is ready to run. It might have already been replaced, saving you the trouble.

[Larry D]

That's what I needed. My thinking exactly...maybe it's been recently replaced.
Thank You very much!!

[Shaughn]

... My opinion again, but the small can of Por15 sealer is pretty skimpy for a large GS tank – I recommend two cans to make sure all the surfaces are coated. It’s only an extra $10 or so but will provide assurance the entire tank is coated.

Hope this helps and good luck.

Or you can accidentally order the car kit, and have more than you need!
Oh well, the extra marine clean and sealer will go to good use. I'm still 50/50 on the Sta-bil equivalent.
Probably could jack the thread on opinions on that alone. Let's not. ;-)

So I'm going to use my old (junk) petcock, filled with cured silicone, to seal the bottom through this process. Anyone have a best practice for sealing the top (filler) hole? The cap on my 78 is pretty damn basic, but I still don't want to replace it.

[Jaguarjoe]

Anyone have a best practice for sealing the top (filler) hole? The cap on my 78 is pretty damn basic, but I still don't want to replace it.

I used "expandable SBR rubber plugs" from McMaster-Carr to plug the filler hole and to plug the sender hole. The little 'ears' on the sides of the filller hole were plugged with modelling clay. To plug the petcock hole I made a small blanking plate and just screwed it into the tank with a gasket to make it tight.