Friday, 22 December 2017

Fuel Tap Leaks

Following on from the replacement fuel filter I made here, I wanted to show you how I have renovated the double plunger taps fitted to my Ariels.

The plungers fitted to these taps are a simple design with a few variations. There is the plated knob, which may be round and knurled or hexagonal; the knob has a short shaft which has a milled groove, aligning with a peg in the tap body (to stop it coming out), and this groove is usually straight, but may be milled with a dog leg such that you can turn the knob to avoid inadvertently shutting off the tap. Fitted inside the knob is a brass inner shaft, of about 5/32" diameter for most of its length which is provided with a short section of larger diameter, to fit inside the tap body and to carry the cork.
Lastly there is the cork - a cylinder shape fitting tightly inside the tap body and around the inner shaft.

Here's a selection. these are all post war, and came to me from John Mitchell of the AOMCC.



Now, these taps are pretty reliable if you know what you are doing when you set them up. The corks wear, and they dry out leading to leakage but if you keep them in good condition they work well. If you have a leaky tap, first consider what you have been doing with the bike. If for example you drained the tank over winter, or the bike has been out of service for a while, or you just bought the tap off eBay try letting the plunger soak in a puddle of petrol for a while, or immerse it in a pot of boiling water for a few minutes to rejuvenate the cork. This approach has restored many taps to working order.

If you have to replace the corks, you need to remove the inner shaft using a punch - a 3 mm or 1/8" punch will be fine. Locate the mushroomed end of the inner shaft and place the knob, shaft down, in the jaws of a vice.


Tap the mushroomed end of the inner shaft with your punch and drive it out


You should have the plunger in two pieces:


Replace the cork. Check that the new cork has a hole that is on-centre all the way through, and that the ends are square - a lot of them are poor quality. Check that it is solid and does not have any dark grooves in the cork that are going to cause leaks.

Check also that it is the right length. The short length of MIG wire in the picture below has two bends in it - one to indicate the open end of the tap and one to indicate the location of the fuel port drilled through the tap - the port that the cork will shut off. You can see that the short cork fitted to the tap has no hope of covering up the holes, but the longer new cork will cover the holes nicely.


Reassembly is simple - fit the new cork over the inner shaft and press the tap together in the vice. Wet the cork in petrol and try it in a tap - it should slide but be quite stiff. Up end the plunger again, and use your punch with a hammer to slightly swell the small end of the inner shaft, retaining it in the tap.

Prewar, the tap plungers were made so that you could adjust the corks and the reassembly sequence is a bit different. This is a prewar plunger, though not in it's own tap; the inner shaft has a 5/32" BSW thread (yes, really) retaining it in the knob.


The shaft has a screwdriver slot and a lock nut, so when you slacken the lock nut you can turn the shaft and knob independently and compress the cork, improving the seal. The lock nuts are often missing, but early Meccano nuts are identical and readily available from specialists; they are a 5/32 BSW thread, but the hex is designed (or maybe just fits) 4 BA spanners.

There is a note of caution here though. If the locknut is absent, the thread damaged or just not tight, my W/NG is perfectly capable of loosening the tap cork after a fast run. The result of this discrete self-destruction is a strong smell of petrol in the garage and a drip tray curiously full... The moral of the tale of course, like most things with old bikes, is that nothing is 'fit and forget'.

But what if you have no plungers? Indian-made plungers are readily available on eBay and the ones I have seen use long M4 screws for the inner shaft. These are again of highly variable quality - the ones I have are plated very well, and look good - but of the five I have, only three have the inner shaft hole in the centre and the corks are way too short...


Usefully though, they can also be made adjustable. I made this one using a long brass M4 screw, with a slotted head filed flat and an M4 lock nut.


Once refurbished, these taps are very reliable. Attach them to the tank with a Dowty sealing washer:









Thursday, 21 December 2017

Petrol Tap Filters

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.

These are pretty simple to make if you are reasonably adept with a soldering iron. Start with 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.


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.

Monday, 11 December 2017

Power to Weight Data

I've been meaning to look at power to weight ratios for a while, mainly since the PO of my SQ4 delivered it to me saying 'I can't see myself using this, it's a big bike and way too heavy for me'. I thought I would look around at some modern bikes and see how heavy it really was, and whether I was going to be able to ride it into old age.

So the table shown here lists a few bikes of interest to me, with their fuelled-up weight in pounds, seat heights for some and power to weight ratios. Look at some of the older bikes & how they compare with some newer ones!




Here's the power to weight ratios charted. enjoy figuring that out, I will replace the chart with one that is easier to read!

Wednesday, 6 December 2017

Imposter

Know what this is, my fellow Ariel-junkies?


This is a Triumph 3HW. Know what carburetter that is? It's a Amal 276AD/1J. Why am I telling you this? Look at this picture:


Yes folks, that is also an Amal 276AD/1J, fitted where my Ariel's 275B/1J should be. This is interesting, because this is the carburetter my bike came to me with, and it is jetted (120) as the 275 would have been; the larger 276 would have used a 150 - to match its 1" choke (the original W/NG carburetter would have been 7/8"). No doubt this came from another of the thousands of military bikes floating around in Italy, or some ARAR compound when my bike's original 275 was pinched or wore out - or maybe it was changed by the Army whilst the machine was in service. We'll see what cutaway & needle jet it has when we get it apart.

Tuesday, 5 December 2017

Carburetter Rebuild

Regular readers will know that there have been a few challenges around the carburetter recently, and that I've started poking around in it.

The first sign of trouble was on the overrun, heading downhill into town with what felt like fuel starvation. A couple of days before, I had run out of petrol on the SQ4, through my own fault (the SQ4 has no reserve tap, a long story) so I was congratulating myself for my inattention again. Pulling on the reserve tap made no difference and limping to my destination saw the tools out and a chunk of debris removed from the main jet. I went home with the jubilation that only a roadside repair can provide.

I started wondering why the bike was quite so slow. Investigating the carburetter slide revealed it wasn't opening fully as previously reported:


The investigation also revealed an uncomfortable tendency for the slide to stick caused by a non-standard throttle return spring, something that showed up in the shop but not thankfully on the road. The carburetter would need some investigation soon.

And remember that blocked jet? That came back to haunt me while coasting downhill into a village near here, when everything started popping and banging, spitting neat fuel back out the carburetter. I limped along for a while with a wet knee, eight-stroking (I thought only Bantams did that?) eventually realising that going home was not really an option, because after all what would I have done if I had been hundreds of miles away?

Pulling the tool roll out, I took the Amal carburetter spanner and removed the jet cover or 'Float Chamber Holding Bolt' to check the main jet - which wasn't there. It was sitting, loose, in a puddle in the bottom of the jet cover.

Perhaps someone didn't tighten it properly? And while you're at it, that fuel leak you have been complaining about, that you thought was the float valve not sealing? Perhaps you ought to tighten the big nut on the bottom of the mixing chamber?

So anyway, the carburetter is back together, not leaking and the bike is running happily with the needle in the right notch. However, we definitely need a new throttle spring, so we better get on to Burlen Services. Investigation of their website reveals there is a short spring and a long spring, but which one?

Tuesday, 28 November 2017

A little maintenance

The W/NG, since I'm shaking down and it is at the front of the garage, is my go-to bike at the minute. Since I made this list I've done a few jobs:
  1. Grease the forks & replace the missing nipple - done
  2. Maybe replace the fork bushes - not done
  3. Tighten the brake torque arm anchor or weld it in - done
  4. Make a T-bolt for the exhaust clamp - done
  5. Adjust and lubricate the primary chain - done
  6. Have a look at the clutch - not done
  7. Change the regulator to a V-Reg - done
  8. Fit a couple of transfers - done one...
I had a nice little trip out a couple of days ago to test the exhaust, which was great but the bike is not very fast and I'm not satisfied that I've got it running as well as it could


I noticed that the carburetter slide was not reaching full travel for some reason, and that the plug was pretty dark. It's also had a bit of an oil leak from the inlet rocker shaft, which as you can see has heavy flat washers fitted over the banjos and the fibre washers. Not surprisingly, the oil leaks down the threads and comes out under the nut.


So what to do? What we always do in these situations - ask an expert, which always means someone in the AOMCC. In this case, a post to the forum yielded lost of useful information including this from Paul Jameson:

The correct assembly is as follows:
  1. Slacken off the screw on the opposite end of the rocker shaft from the banjo.
  2. Fit copper washer, then banjo then copper washer then acorn nut.
  3. Tighten acorn nut.
  4. Tighten screw on the opposite end of the rocker shaft from the banjo.
And this is why. Paul Jameson again:

The rocker shaft has a shoulder which goes against the inside of the rocker box so with the method above you tighten the nut, banjo and washers against the shoulder. The rocker shaft is sealed so that oil cannot emerge under pressure at the screw end. Hence the screw only seals against oil running along the outside of the rocker shaft.

So, undo this screw on the opposite side:


And you can see the end of the rocker shaft. Grip this with a very large screwdriver or a washer in the slot, and tighten down the acorn nut on the other end, against the fibre washers, then replace the large screw and snug it down into the milled recess to seal the rocker box.



Next, have a look up the inlet tract with the throttle fully open. Yes, I know I can see the carb slide:


Something odd here!

Let's have a look at the slide and spring. First off, the needle shouldn't be in that position, which is why my plug is sooty -  it should be in the middle slot; secondly, that doesn't look like an Amal spring and fiddling around with it allows the slide to move up fully. Shame it doesn't return properly.... It looks like it has its original brass slides though.


We'll have to get a new spring at least.

Turning to the back end, the chain has loosened off a lot. The primary chain is fine, and the chain is easily tightened up using Ariel's handy adjusters; odd spanner size though, the hex appears to be 3BA.


So that is that for today - we need a couple of seals for the rocker shafts, a new carburettor slide return spring and some front wheel bearings for the SQ4.





Thursday, 23 November 2017

Exhausted by all the noise

Blatting about North Norfolk I've become aware of quite how loud the W/NG is, partly due to its original silencer and partly due to the poor fit of the exhaust pipe, which is well and truly battered, to the cylinder head.

I've no intention of doing anything about the silencer, or the battered nature of the pipe since they are irreplaceable original parts, but I must fix the joint to the head as it is leaking fire and smoke with every other piston stroke. You might recall I made a new exhaust pipe clamp which has done well but it cannot deal with the fact that the pipe does not fit...


I looked at various ready made mild steel exhaust pipe bends available at a well known internet auction site, before I twigged that I had an old exhaust header in the loft, the perfect diameter:


And the perfect shape:


I cleaned it ferociously with emery tape:


I need about 45 mm of this tube to reach the head, using the full length of the cast stub. The exhaust has had a repair in the past which was not aligned correctly, leading to the leakage problem, but leaving 5 mm of this old repair piece in place means I do not have to weld to 75 year old steel.


I've put a ring of masking tape around the old & new tubes, to show where I have to cut and to keep the cut square.


Clean the inside:



I've marked the outside of the bend with a Sharpie to make sure the pieces are aligned as I go to tack up.:


Now tacked in about 6 places, we go to trial fit. Not too bad the first time, but ideally needs more angle - I needed to cut a wedge out, to bring it closer to the head at the top.


Now fully welded & a first coat of paint applied:


Clamp added:


Just got to finish painting it now.



Sunday, 19 November 2017

Sunny Autumn Day 2

Cley village this time, along the North Norfolk Coast & back by a round about route. The W/NG is the machine of choice at the moment, partly because it needs shaking down and partly because it is so good at these roads - but also because it is at the front of the garage.

Here she is at Cley Church:


Shes starting and running quite well at the minute, though I'm really not convinced the ignition timing is correct and the exhaust to head joint is leaking. This needs a proper repair, as the straight piece of pipe welded on by PO is at the wrong angle and hasn't a hope in hell of making a gas tight seal...



I have a suitable bit of pipe in the loft, from an old SQ4 Two-into-One. It got the right sort of curve:


More later. Hopefully this week, though I am loath to take it off the road