Monday, 22 July 2019

Petrol Tap Filters

Updated from December 2017

Many of the fuel tanks we have on our bikes are not in the best of condition and may be flaking rust or paint from inside, or worse, your tank liner may be in the process of falling to pieces. It's essential to have a good fuel filter.

Here are a few I made earlier:

Most of the fuel taps I have acquired have had either missing or holed filters, and, having had very limited success with the inline filters on the market (poor fuel resistance in plastics leading to cracking & cloudiness, or a ridiculous flow coefficient leading to fuel starvation) I have set about replacing the missing in-tank filters. This is typical of the damage you will find, if not a lot worse:

These are pretty simple to make if you are reasonably adept with a soldering iron. Start by removing the old one. I use a kitchen-type blow torch for this, which is plenty hot enough for sweating soft solder:

Hold the intake tube with a pair of pliers and twist it gently when the body is warm. It should come free quite easily

Look for the finest mesh you can find. The originals are a very fine copper mesh which is easy to obtain (though the mesh in the pictures is actually brass). Cut a suitable rectangle with scissors.

Start to form the cylindrical shape around a pencil.

You'll see that the final size for the filter on this double-plunger Ariel tap is very close to the diameter of an AAA battery:

I use a chamfered edge on an old credit card to form a tiny lap joint on both edges of the gauze, like I did with the oil strainer on the SQ4:

I then roll them around, mating up the lap joint and folding it down tight on the AAA former.

You can make a simpler lap joint like this:

Solder the joint with a small iron:

Flare the end to fit into the recess on top of the tap:

Have a good look at the recess on top of the tap. Make sure you clean out the joint of all goop, old fuel, rust and old solder. We are going to tin this area and sweat the new filter in.

Put the main feed pipe back in and trial fit the filter:

Now, push your AAA battery former up to the other end of the filter and form the closure:

Lay some solder onto the flare:

Lay a little more solder onto the end closure:

Flux the top of the tap and using a small blowtorch (the type you might use in the kitchen) apply some solder all around the joint, without the filter in place. Let it cool and clean it up and have a good look to see that it has run all the way around, then add the filter. Reheat the tap just sufficiently to melt the solder , and the heat should transfer to the solder ring around the filter flare allowing the two to fuse.

You might notice that this tap is fitted with a 3/8" BSP Dowty seal - makes a better job of sealing that joint than a fibre washer.

If you still have problems with your tap, check my post on replacing plungers here.

Thanks for reading, and I hope you found it useful.

1 comment:

  1. I nned make the same filter to put in my Ariel WNG! Thanks for sharing