Copper fuel lines

I have used 1/4" copper brake pipe for fuel and oil quite successfully. For vibration issues, a corkscrew section in the copper line or a short ordinary flexible section at one end seems to do the job. Halfords fuel injection flexible pipe has so far been proof against ethanol in petrol.

I made the fuel lines up for my 16H and was surprised how easy it was. I used soft copper tubing. It's supplied pre-annealed on a roll. Mine came from a trader at Beaulieu. I think that the car enthusiasts use it quite a lot. Based on the fact that the old lines which I dismantled sweated apart quite easily, I soft-soldered mine.

There is a suggestion that chrome plating embrittles the pipe and in view of this and the fact that I wasn't looking for a concours finish on a WD bike with lots of original Norton dull chrome, I simply tinned mine all over and it gives quite a nice dull grey finish.

I tried bending initially using the expensive pipe benders from work which are perfect on thick-walled hydraulic tubing but couldn't avoid a flat on the bends so I reverted to a sort of 'Uri Geller' technique of gently forming the bends in my hands. It was straightforward if enough length was left to trim afterwards and I found that I could achieve 90? on quite a tight radius.

The spiral on mine has an inner diameter of 34.7mm - I rolled it around a Commando fork stanchion which seemed to scale up OK from an old photo.

[IMG]http://i248.photobucket.com/albums/gg164/commando16h/NOC/FuelTankabove_zps31ca575f.jpg[/IMG]

If you're not going for originality, some WD Nortons used a double banjo on the float chamber with a straight length of flexible tube from each tap. It's tidier than a flexible system using a Tee and a single banjo.

Chris - the curly pipes in your picture look very pretty but the curls on my 16H are horizontal and not vertical - so mine look a bit like saddle springs. That way they won't have air locks.

I don't have a convenient photo here but should be able to take one tomorrow if it's of use to you. They are original but currently parked in a box.

Copper pipe is usually sold in 'annealed' condition so it's easy to bend cold - once. It's easy to anneal it again if you have enough heat - red hot and let it cool or quench in water - it makes no difference. Hope it has no fuel inside...

Someone else might know better but I'm fairly sure the wall thickness of the smaller tubes allows them to be bent without buckling the walls. Tubes can also be bent after being filled with dry sand (playpit sand) - but maybe that's not too clever for fuel (or oil) lines...

Copper pipe of that diameter can be bent without a spring or sand inside. Have the coils in a horizontal plane, not verticale or you will get air locks and a weak mixture. Dont ask me how I know or what the results of that weak mixture were.

Use tinmans plumbing solder and flux, not electrical solder which is more brittle and will crack easier. Make sure the pipe and inside of the fittings are imacuatly clean before heating and soldering.

Finally, flush the pipe out with very hot water to remove any flux/solder that may be inside afterwards.

Photo of the pipes on 1937 bike - fairly sure they are original.

All petrol pipe nipples should be silver soldered as soft solder will fail eventually. Maplins can supply the solder and the special flux powder. The pipe and nipple must be perfectly clean, then apply the flux as a thin paste (made with a drop of water stirred into a pinch of the flux powder on a clean plastic lid. Apply flux carefully with a matchstick as the silver solder will go exactly where the flux is and nowhere else. Heat with propane until the nipple is just reddening, with the pipe in place, and touch the silver solder onto the joint and in it goes, forming a strong neat collar round the edge. This anneals the pipe, too, and silver-soldered pipes can be re-annealed without damaging the joints if they get hardened or need bending. 1/4 inch copper bends easily by hand round a suitable cylindrical object (beer bottle!). Don't forget to put the joint nut(s) on the pipe before you solder the last nipple on! Wash the pipe out and polish it up after all this.

Silver soldering is the way to go, though I have soft soldered them with success as long as the pipe is inserted deep into the fitting to get plenty of surface contact. One thing with silver soldering copper tube, the heat will form an oxide (scale) on the internal wall,whichWILL eventually flake off, causing havoc with the float needle seat and the main/pilot jets. Don't ask how I know.

I am sure that this is a dumb question. Are we talking 5/16" or 1/4" for fuel pipes. both sizes seem to occur.