BMW R65LS Restoration


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.


To do