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Old April 25th, 2011, 04:02 PM   #1
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Tank sealer

Well after 25K miles my tank has succumbed to the dreaded deformation. My tank looks fine it's just a little longer.
Ducati is replacing the tank. I'd like to do something to the tank to keep this from happening again. Any ideas?
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Old April 26th, 2011, 02:15 AM   #2
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Location: H Valley NSW Oz.
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Warning: wall of text below...

Yes, another thread about gas tank expansion/warping, but this one includes tips on applying an internal coating if you want to do it yourself.

A little background: I noticed some odd and barely noticeable wrinkles in the tank last summer, about 9-10 months after I bought it and about 5000 miles. Over the last six months the warping has become more significant. It's still not immediately noticeable unless placed aside a good tank, whereupon it becomes very obvious. The tank has expanded slightly and was clearing the triple clamp on full left-lock by less than a millimeter. The paint has begun to sort of "pull apart" along the top, as well.

I'm continually impressed by the service department at my dealership - GP Motorcycles in San Diego. They put in a warranty claim and got the new tank quickly. I discussed the prospect of coating the tank with one of their service guys. My concerns were voiding the warranty (he assured me it would not) and the logistics of getting it done. They were willing to coordinate shipping it somewhere to get the coating done before installing it, but when I mentioned the possibility of doing it myself (which I wanted to do from the beginning but figured would be impossible for warranty reasons) they were all about it! They saw it as a potentially excessive time-consuming job, anyway. I pulled my warped tank and brought it in, but when it became obvious that the tank would have to be cut to remove a couple bolts that were installed with too much lock-tite (go figure, Ducati...) they let me keep it!

This is the product I used to coat it:

Caswell Inc. - Epoxy Gas Tank Sealer

The instructions say that it will coat two 5-gallon tanks, and to divide the parts in half if only doing one tank. However, you will want to use the entire contents due to the elongated and very irregular shape of our tank which results in a lot more surface area compared to a 5-gallon Harley tank.

The instructions also recommend to dump some drywall screws, dish soap, and hot water in plastic tanks and swill it around to clean and rough up the surface. I was skeptical about this step since my tank was brand new and clean, but I did it since I didn't want to risk anything that could make the coating fail. Fortunately I had the foresight to get an exact count of all the screws I put in the tank so I could be sure I got all of them out. In retrospect, I would not recommend doing this at all if you have a new tank that's never had fuel in it. The surface is already clean, and the plastic is tough enough that the screws don't do much to rough it up. The main reason not to do it, though, is that there are so many crevices inside the tank that the screws get easily jammed in places that you'll never be able to reach or even see from the filler port or the fuel pump port. I spent probably 2 hours nervously shaking the tank, removing and counting screws until I got them all. Then you have to get the inside dry - and you can't see into the deep recesses along the sides so you just have to go overkill on the drying time. I set up my shop vac to blow into it for about 30 minutes. I'm pretty sure this completely dried it, but I still let it sit overnight since there was no way to be sure that there wasn't an errant water drop sticking in some crevice. If you do this, be sure to put a towel or some sort of filter over the end of the shop vac hose so you don't go blowing bits of dust and dirt stuck to the inside of the hose into your clean tank.

The coating epoxy is thick and has a relatively narrow range of optimal operating temperatures. Too cold and it will be way too thick to flow and coat effectively, too hot and it will cure too fast. Fortunately I'm in so-cal and it was a perfect 70 degrees. I made some block-off plates for the filler port and the fuel pump opening. I used a couple plumbing fittings on the fuel pump block off plate to make a place where I could dump in the coating and quickly cap it off. I wrapped the whole fuel tank in saran wrap - this is critical as you will likely end up with a drop of sticky epoxy on your hands at the exact time you will need to be handling the tank to spread the coating.

I originally mixed only half of the epoxy per the instructions, but was nervous about getting good coverage on the odd-shaped tank so I quickly mixed and added the rest shortly afterward. I'm glad I did this.

Once the coating is dumped into the tank and your fill port is capped, all that's left is to slowly rotisserie the tank for the next hour or so until it's set up. This is nerve-wracking because you can't see how the coating is spreading. You have to guess based on how it flowed as your poured it into the tank. After about 15 minutes it has probably gelled up enough that you can remove a block-off plate and look inside to gauge your progress, although you can only see about 75% of the interior of the tank (a dentist's mirror would have been great!). The coating is pretty much clear, so that doesn't help either. It would be a huge help if it were dyed some color. The instructions say that you will need to dump out any excess. I might have had about 2-3 ounces of excess, but I just continued rolling it around the tank to get a better/thicker coating. After being satisfied that the coating was spread sufficiently I let it sit for a while and came back to find a few semi-cured thick strings of coating that had dripped from the top to the bottom near the filler port. The coating was still sound and I was able to cut these out since it was still rubbery.

All in all it took me about 2 days to do the coating with all the drying and curing time. It was more difficult to do than I expected. If I were to do it again, I would research adding a dye to the mixture and I would get a dentists mirror so I could see all of the inside of the tank.

Judging by how difficult it was to cut the excess coating away from the filler port so the filler could be re-installed, the bond was pretty good - roughly twice as strong as say duct tape sticks to metal - but I don't think it exactly fuses to the plastic. Chipping away that coating around the filler port probably left some small spots of tank plastic that will be exposed to gas. Only time will tell if this is a problem.

I'm concerned that the cured coating might be less pliable than the tank material itself - meaning that it could crack and chip if the tank was flexed and clog the fuel filter.

Overall I give the coating an 80% chance of being effective over the life of the bike. An aluminum tank would obviously be the ideal solution, and I would be willing to lay down some significant money for one.

I didn't get any pictures of the actual coating process since it was time critical, but I'll post some side-by-side pics of the old and new tanks later since I've noticed there aren't many pics showing warping of our tanks.
Last edited by zach34; Today at 7:58 am.

Heres the link http://www.ducati.ms/forums/138-stre...ps-tricks.html
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