Saturday, July 30, 2016

Steel fuel tanks and rust - the sort that makes holes and creates much agro

I had a 748 in recently - 20,000km, overall quite clean, purchased a couple of years ago out of Queensland.  It had some marks on the engine cases showing some sort of "liquid from above" staining, and when I pulled the tank there were a couple of small areas of paint bubbling with a wet look about them (never good).  Removing the pump assembly showed the extent of internal rust.  Photos show some of the tale.  The crud around the fuel pump pickup was quite amazing.  The rust holes shown were exposed using a piece of Scotchbrite only, there was no real effort involved.  It's amazing to think it wasn't just pouring out.  I was discussing this with Brad at BikeCraft and he said he has had customers come in to him with tales of no leaks until it dumped a whole tank in seconds from this sort of rust damage.

If your bike has a steel tank, it's important to look inside it at regular intervals.  Make sure the cap recess drain is clear, so any water that sits in the cap recess will drain out, not run into the tank the next time the cap is opened.  Add something to remove water occasionally.  Every time I service a bike I add about 100ml of injector cleaner.  I use Wurth brand cleaner, I think what I get is the imported stuff that you can't buy retail afaik.    It's great stuff for cleaning injectors - I've had to reset idle mixtures after road tests sometimes just due to it doing it's job - but it's also good for removing water from the tank.  Metho also will do the water removal job.

Even plastic tanks can benefit.  Sometimes you can get a jelly sort of stuff build up in them, or you get the likes of the Cagiva Raptor, where its plastic tank has a bolt in fuel pump assembly with exposed steel fuel pump wiring.  In a triumphant masterstroke of engineering design, those terminals sit at the lowest point of the tank.  Right where the water collects.  Genius.  Luckily you can get the complete plate assembly from Suzuki as a TL1000R part - at around $800 (from memory) it's about half the price of the probably now non existant Cagiva part.

Another thing I see with plastic tanks is their cap recess drains blocking at the little screw in aluminium barbs in the bottoms of the tanks.  Often the rubber hose routing after the barb is such that there is an upward run causing water to collect in the barb.  They just fill with white corrosion, which can go surprisingly hard.  I find the easiest way to clear them is to run a 2.5mm drill through them, which also illustrates how small and easily blocked the hole is.  Best to remove them before you go drilling into them while they're mounted in a plastic tank, but then again I've had a few break off before coming out.  I now keep a couple on the shelf.  Any of the late model bikes with plastic tanks can suffer from this, including Aprilia and Moto Guzzi.


jrh001 said...

Hey Brad,

"Every time I service a bike I add about 100ml of injector cleaner."

What about older carby models like M600 running on standard fuel? What's the best way to prevent rust in the tank? I always store the bike with a full tank. What additives would be suitable?



Brad The Bike Boy said...

I use the injector cleaner in anything. It's just a collection of alcohols designed to remove water and fuel gum.