BMW R65LS Restoration

Tank

The filler cap was firmly rusted in position.  I had to force it off and in doing so broke the locking mechanism.  After detaching the plastic lock cover I resorted to an old screwdriver and hammer to unscrew the filler cap.  I managed to put the cap back together again so it looks OK, but the lock will never be operational again.

Removing the cap revealed a very rusty interior to the tank. I drained the tank into a petrol contained and removed the petrol tap.  This is some sort of alloy or maybe zinc and would almost certainly be damaged by electrolysis or vinegar. I found the petrol tap blocked by rust in the reserve position so I disassembled it.  I wish I hadn't. The internal spring made it a pig to put together again.  I'd recommend trying poking a piece of wire through before taking it to bits.
I wrapped some plumbers tape around an old pencil and used this to seal the petrol tap hole.

 I considered filling it with vinegar and leaving it but instead I decided upon electrolysis.  I used an old socket spanner suspended in the filler hole for an anode and the tank as the cathode.  The tank was filled to the brim with a solution of washing soda and left for a day.  I did however taking the anode out and clean it every two hours or so.  After cleaning the current flowing was around 4 amps (from a 12V supply).  It dropped to around 0.2 amps within around 15 minutes though.  

When I emptied it after 24 hours, lots of rust flakes came out with the water - just what I wanted.  A blast inside with a pressure hose released more, then the water came out clean. I pointed a hair drier inside to dry it out as much as I could then I quickly put the tap back, put the petrol back in the tank and give it a good shake to remove any residual water.

The outside of the tank could do with another coat of paint.  That's for another day.

Contents


Background
To do
Rust
Tank
Seat
Exhaust
Links




Photo-Electric