04 R1150RT Fuel Tank

[bewareboy]

Spring project ... new internal fuel lines, new fuel pump / sock, new fuel filter and new a gaskets all around. Everything going well. Internal tubing was original and seemed to be in better shape than I anticipated it would be. Anyway, changed it out since it was ~12 yrs old. New pump, vibration damper and filter all went together pretty much like I've heard on the forums. My only question is that since everything was out of the tank, I siphoned all the remaining gas out to dry out the tank and try and get the fine debris out. Seems like very fine material, dirt, sand, small gold flakes, etc.. Thought this may be from the gas pump nozzle scraping on the gas tank filler next or the fuel pump/filter plate which are goldish colored? Anyway while reaching into the tank through the fuel pump/filter plate boss, I noticed a small diameter (~3/8" to 1/2") silver item on the right hand, inside, side wall of the tank. Item is on the center to left hand side of the pics. This is somewhat near (bit forward of) the fuel level sender mount boss. I have some pics, but since I had to put the camera in the tank, this item was pretty close and the camera was not focusing very well. Maybe it will be evident to the more educated on the R1150RT tanks. The feel of it to my finger was smooth, no raised edges, but the center felt a bit soft, like the protective foil cover on many fuel additive bottles. Anyone have any experience with what this may be. All I could think of was that it covers a manufacturing defect, like a void or large pore in the plastic. The opposite side of the tank wall (outside the tank) does not have any irregularities, nut inserts, etc... Thanks,

 

[pauls1150]

Maybe you could reach it with a straightened (custom bent) coat hangar?

I've seen assorted grit inside of tanks; that's why there's a sock on the pump's intake. Maybe it really is the seal from a Techron bottle... If it was a manufacturing defect, I think it wouldn't have gotten through Quality Control at assembly.

 

[bewareboy]

I'll take a look at it again tomorrow. BMW only sent me 36" of vent tubing and according to the installed tubing lengths I need 40"-42" so I should receive that tomorrow or Friday at the latest. I have not buttoned up the tank so I can reach in and touch it with my hand, so not sure the coat hanger would be needed. Will double check if it could be debris. Thanks,

 

[AntonLargiader]

It's probably just a bubble. Seems to be a blow-molded or roto-molded tank, so if the molten plastic had a bubble in it before it was formed, it would look like that.

 

[bewareboy]

So I took the dog out and decided at the same time to look at this again and more closely with a bright light. I think Anton is spot on. This feature is very smooth all around the circumference. Slightly raised in the center. Very thin center. I think this blow mold bubble may be the exact situation. I assume that since this may be a bubble that is why it is a lighter color as there is not the solid, dense, cross-section. My minor concern is if the thin center section becomes punctured or cracked, how big of a void is behind? The outside of the tank shows no visible indication where this bubble or void is. I think my next check will be to put a bright light next to the bubble or void and see if i can discern any lighter color on the outside portion of the tank, indicating a thin wall condition on the outside also. The tank has never leaked, but now that I have played with it a bit, I don't want to initiate a problem. The other thought would be to pop the blister and fill the void with a fuel resistant material with the consistency of a JB weld. Thanks,

 

[bewareboy]

I think final thoughts on this. I took a more thorough look all around the inside of the tank with a bright light and I was surprised to find numerous smaller sized bubbles all over. I also took the bright light to see if a thin wall conditions existed where this larger, original bubble is located I could just barely see some light from the outside of the tank. As an side note, there were other transition location on the tank where there was more light (or thinner wall) condition than at the main bubble location. Again as Anton mentioned this must be a result of the blow molding manufacturing process. I decided to just leave well enough alone, quit messing with and quit worrying about it. Thanks and happy and safe riding.

 

[motorrod]

Tank bubble

C'mon, like all BMW riders,you are uber aware of everything. Every time you smell fuel when you're on the bike, you'll imagine that bubble has failed and fuel is running down the inside of your tupperware!
Try to get that song out of your head!