Hawk Gas Tank Leak

[China Rider 27]

Spent the weekend chasing a gas tank leak. Smell of gas in the garage and noticed a couple of small puddles just behind the kick stand below the battery which is quite a bit aft of the tank. The fuel petcock had a big gas drip on it so thought maybe that was it but gas had just leaked down onto it. I noticed gas on the wiring harness as it comes down to the battery. Took the tank off and I could see what appeared to be some gas around the sending unit. Took the sending unit out and O ring looked good. Tightened it up, filled it up, and took a long ride. Two hours later no puddle in the garage. This morning two puddles and fresh gas on the wiring harness and petcock.

Took the tank off again. I had put a little grease on the tank around the sending unit to protect some rust spots. That looked intact, I mean it wasn’t washed away by gas. The black tube around the sending unit electrical connection wire had gas residue. Appears the center electrical connection fitting of the sending unit has a slow seep, maybe only during or after engine vibration, and it slowly follows the wire down. After researching on the forum I saw another member had a leak near the rear mounting bolt and his tank made contact with the frame. My tank is making contact with the frame at the furthers rear point past the mounting bolt. Might wanna take a look at your tank mounting setup.

I ordered a new sending unit from CSC but I am thinking of encasing that wire connection in JB weld?

[Weldangrind]

I think I'd want access to the connection. I'd use self-vulcanizing rubber tape over the connection instead. 3M makes it and it's readily available.
Maybe put a little grease on the o-ring and see if it stays dry.

[China Rider 27]

The connection ends in a plastic piece with a rivet in the center to the flange so it must go through to the other side of the sending unit. Best I can determine it is leaking through that rivet very slowly down from the connector to the wire. But I am gonna take it apart this weekend and look at it from the other side and fill it up while its off the bike and see.

[dpl096]

I agree with Weld. I would certainly want access to that connection. I'm hoping your replacement fixes the problem

[GronkFries]

You probably have issue identified, but to make sure I would pack a little bit
of duct seal around the rivet & wire as it is removable or go the distance with a dab of Seal All which is petroleum resistant. I use that to seal airboxes and other tough gassy components. It's the best.

[China Rider 27]

Originally Posted by GronkFries

You probably have issue identified, but to make sure I would pack a little bit
of duct seal around the rivet & wire as it is removable or go the distance with a dab of Seal All which is petroleum resistant. I use that to seal airboxes and other tough gassy components. It's the best.

Thanks for the suggestion. I will check it out. Seems to me best place to seal would be from the tank side of the sending unit. I may try to seal it from that side.

[China Rider 27]

This looks like good stuff too. I will keep it in mind as I go.

[China Rider 27]

Confirmed... it is leaking out of the yellow sending unit wire crimp connection. That yellow blob on the connection is actually a drop of gas.

[CSR_Sprocket]

After the last snows melted this year I went to start up my 2015 Hawk and found that the tank was dry. I though I'd filled it an put an ounce or two of Stabil in the tank before putting it up for the winter.

I found some gas dripping off the lower tank seam on the right-hand side. Without taking the tank off I poked a flashlight and saw a stain running down the inboard right-side of the tank. Removing the tank showed that a corner of the ignition coil was rubbed flat on the top/rear edge. There was a matching depression on the inboard side of the tank. Though I didn't actually see a crack in the metal, it seemed like the most likely culprit. Especially after I removed the sending unit and found the O ring to be in very good shape. The ding showed up better after I primed the tank (this is my first attempt at attaching a photo to a post).

So I decided to use JB-Weld as "Bondo" over the ding plus seal the inside of the tank with KBS "Gold Standard"

Because I'm stoopid it took me three weeks to clean the inside of the tank with first detergent then phosphoric acid (kills rust). I inspecting the tank from both the filler neck and sending unit port i saw patches where the acid had removed paint (!) from the inside of the tank. Several treatments with Kleen-strip Aircraft Paint & Epoxy stripper (very nasty stuff) removed most of that. A bath with muriatic/ hydrochloric acid, then a final bath with phosphoric acid (I'm a fan of phosphoric acid - I think it's the active ingredient in Naval Jelly). I then the tank it dry in the sun for several days (bringing inside to avoid dew in the morning)

As to sealing the tank, I'd used Kreem in the past with good results. To mix things up I decided to use KBS "Gold Standard" this time around. I now highly recommend Kreem over KBS. It was impossible to open the KBS can without destroying the lid. I literally had to punch holes all the way around the top to cut it off. Because the stuff cures so quickly when exposed to air, there's no way to apply a 2nd coat. Kreem on the other hand comes in a plastic bottle and they recommend applying a 2nd coat. You might even use the remaining sealant on another tank...

Geez, I talks a lot!

I put everything together today. i set the tank over two sawhorses with a huge catch pan underneath. I put a gallon of gas in and raised the level above the nick that I first suspected was the leak. No leak. Yippee!

I put another gallon of gas in and within a few seconds I see drips coming out the end of the anti-chafe tube that encloses the sending unit wires. Just as China Rider 27 points out with both excellent writing and photography, the leak is coming from the hot wire that passes through the sending unit and into the tank. As for photos, for the life of me i couldn't get the photo of the drip to not upload sideways...

To be clear to other replies to this post warning not to enclose this connection for fear of losing access to it, this connection is not a serviceable. The only way to remove it is to drill through the sending unit or to grind off the head of the rivet with a dremel tool. Yes, most of us do these things as a matter of course. That's why our neighbors consider us to be either a genius, an engineer or bonkers.

But GronkFries to the rescue! I'd never heard of Seal-All before reading this post today. A new sending unit from CSC is only ~$15 to Albany, NY plus shipping $5-10 usps shipping). A 2 oz. tube of Seal-All is $5 and will arrive by Monday. So I'll order both.

BTW, shipping/handling rates from CSC have dropped tremendously. February of 2019 I ordered 2 spare keys from them. The cost for the keys: $3.90. The cost for shipping & handling: $15.19 (!). The cost for 2-day usps priority today was about $10 (~$24 for part + handling + shipping). Yay!

And yes, I do talk this much in person as well. A friend of my recently told me that I'm loquacious. I had to look that one up. In doing so I determined that I'm more garrulous than loquacious.

-Corry-

[CSR_Sprocket]

I finished draining the tank an hour ago then I inspected the bottom of the sending unit. Photo included. Look closely at the nylon fitting that the positive (+) wire passes through into the tank. It looks like it's partially melted because it's dissolving. I guess this batch of plastic wasn't fuel resistant. At least not three to four years down the line.

I spoke with Mat at CSC a bit ago and both the sending unit and a replacement front brake master cylinder are on their way.

Master brake cylinder? The last time I rode the bike I rode up to a stop sign and grabbed the front brake lever like I normally do. The most powerful sphincter in my body involuntarily puckered when the lever bottomed out against the throttle grip with no resistance whatsoever.

Oh, I love reliving moments from my younger years when, in retrospect, I'm surprised that I survived.

-Corry-

[NzBrakelathes]

Ethanol fuel? Eats everything?

[China Rider 27]

I had ordered the CSC sending unit for $25 so I put that in. Notice it has white sealant over the top of the plastic connection. They obviously new something about improving that connection. If I would have had Seal All close....

[Frag2]

I used permatex Gasket Maker fuel resistant--Motoseal, put it inside the tank around wire let dry, bitch had long dry time think 24 hours gray in color, 1600 miles so far no leaks

[culcune]

Originally Posted by Frag2

I used permatex Gasket Maker fuel resistant--Motoseal, put it inside the tank around wire let dry, bitch had long dry time think 24 hours gray in color, 1600 miles so far no leaks

I am trying to remember if this is what I used a few years back and my leaking TMEC 200 Enduro. I found it at True Value and it was made for gas tanks and the like; gasoline and oil resistant. My actual tank was leaking--never leaked again once fixed. I don't even think I even had to drain the tank.

[CSR_Sprocket]

Yeah, I know. I'm beating this one to death.

Here are photos of a sending unit I received from CSC. I void warranties with careless abandon so the first thing I did was take the cover off the wiper and variable resistor (I had to look up what they are called).

Notice the notch in the Oh-ring. No, mom & dad, I didn't break it. I promise! It was broken when I opened it.

To be fair it's not the fault of CSC that the O-ring on this part is defective. Chances are a fair percentage of them coming across the water have flaws like this. And given what we know about the rubbery parts on these beasts (accordion fork boots, brake caliper pin boots, etc.), that's a prime place for solvents to start eating away. Once the material is compromised enough, the only thing holding the gas in the tank is, well, magic I guess.

My tube of Seal-All arrived from Amazon the same day as the sending unit. I did my best to inject the stuff all around any part that gas could find its way through. If you ever use this stuff beware that it's extremely low viscosity. Meaning that it will drop all over the place if you're not careful.

Though I doubt that gas will leak through this conduit for some time to come, I'm hoping that it never leaks again. In my lifetime or whomever takes up the torch after me.