Model A - carburetter investigation

In a spare moment while waiting for parts I thought I would have a look at the carburettor provided with the Model A kit. I've not touched it since it arrived all those years ago:

In the last couple of days I have removed it and giving it a good clean so that I can discover what's missing and what's broken.

It's the original carburettor and is pretty worn but it cleans up well:

Standard fitting for the 1930 Model A is a 6/112 carburetter, now called a Pre-Monobloc, which is 1" throat diameter, and here is the evidence:

According to the Amal book, jetting is as follows:

• Size: 1"
• Main Jet: 4/042-160 (still available new)
• Pilot Jet: none
• Needle Jet: 4/061-106 (still available new)
• Needle: 6/065, position not recorded (still available new)
• Slide: 6/0524 - that's a #4 cutaway, or 1/4"
• Float chamber: 14/004

The slide is really bad - probably the worst wear I've ever seen, but it's the original #4 slide. The grooves around the top of the needle are in pretty poor shape too - we should expect this and the needle jet to need replacement

The choke slide spring appears to have been cut short - fortunately I found a spare one in the carburettor bits box.

The float chamber appears to be correct - I didn't expect the bowl to be held by those two brass fittings at the bottom - there must have been a gasket in there

Initial observations:

• The main jet is missing
• The needle looks very tired 
• If the needle is tired the needle jet will need replacing 
• We probably need another cable adjuster 
• The slide is very bad which probably means we need a rebore from Joe the Carb.
• We need to understand how the float chamber fuel feed was sealed - possibly by some sealant in the thread

That's it for now - it's back on the bike and we can start some other jobs.

Model A - on the bench!

 With the Square Four at Tom's house, the initial service on the FH complete and some of the running repairs to the W/NG finished we can swap the bikes around in the workshop and put the Model A on the bench. I've had this bike for 5 years or so and have been steadily making fasteners and collecting bits ever since so it appears very complete although I haven't done any repairs to the broken parts yet.

Let's have a look at a few current pictures.

Five years ago I wrote an article called 'Broken and Missing' which outlined what I found when I took delivery of the bike initially. What follows is most of the text from that article updated to reflect the state of play today. Some of the pictures in the text date from the original article.

Frame

To date, I haven't found any problems with the frame mainly because I haven't dismantled the bike yet. The paint is good, all the threads I have seen have been good or have been repaired in the last few years, but looking at the saddle I suspect the saddle nose mount will be quite worn.

The engine plates are all there, along with a pair of footrests from AOMCC Black Ariel Spares. The footrest bar is bent but is just a bit of 7/16" round bar. I have the two engine plate covers around the dynamo, both of which need weld repairs.

The rear stand came from Ariel Klub Slovakia and I have one of the last of the reproduction Es-way side stands.

Forks

The forks are complete and straight, but feel like they are quite worn - and these forks do not have bushes. The components, with the exception of the grease nipples are all there.

It may be that this bike has been assembled with no balls in the steering head - it certainly wiggles around as though the races are empty. It might be wise to sort this area out first to stabilise the machine.

One of the stay bolt holes in the fork end had a broken bolt in it - I drilled that out and reclaimed the thread a few years back.

Tank

The petrol tank, cap and oil pressure gauge are all there and in nice condition. The cap needs a small repair internally; the tank has a few dents but little obvious rust and the chrome plating is intact. There are three of the original mounting bolts; I will make a fourth. Some of the original mounting rubbers are there, but I have a complete set from Jeff Hunter Engineering.

The knee rubbers and their plates are all there, though the rubbers are thoroughly squashed and unusable. Again I have a replacement set.

The oil pressure gauge pipe and fuel tap are missing. I have acquired a suitable period tap with the correct adjustable corks from eBay:

It's a 1/4" BSP tap and has an adapter. I'll have to make a filter for it.

Front Wheel & Brake

The front wheel needs truing and a spoke replacing. I'm hoping to get away without replacing the original rim, but that will require much closer inspection. The few spokes I have looked at appear sound and the nipples turn - I have dosed them all with Plus-Gas. The wheel turns freely and smoothly.

The brake plate is there - the arm is there and it feels like the shoes are too. I have the brake rod and the torque arm; I've also sourced an adjuster and made the spring box.

You can see that broken stay bolt I mentioned earlier in this picture.

Rear Wheel & Brake

The rear wheel runs true and turns freely, but it is missing at least two spokes. The sprocket, which is integral to the brake drum is worn and will need replacement; the brake plate, arm and shoes are there but the wheel spindle nuts are quite poor, one is missing a spacer and the other is seized on. The chain adjusters were both missing but I have made a new set.

Since I took this shot, I have fitted the rod, made a new rear brake adjuster and realised the cam spindle is very worn. I made a new pin for the rear clevis but the front trunnion is very poor.

Engine

The engine turns over - that is about all I know! It's lost a few fins, and one of the valve caps is broken but I guess that is patina. The timing chain case looks fine. There appears to be a braze repair to the base of the barrel but only an engine strip will reveal more:

There's a lot of broken fins up there. See the big lump of braze?

Primary Transmission & Clutch; Final Drive

The chain & sprockets are there; the clutch looks complete apart from two missing springs and appears to lift when you operate the arm at the gearbox end.

I've seen much worse clutch drums than this:

There are several repairs on the primary chainguard like this, using rivets. The clutch dome is also split. I will probably weld up these riveted repairs as they are not adequately fixing the chainguard in place:

The rear chain guard is there and in good shape.

Gearbox

The gearbox appears to be complete apart from the kickstart spring and it's cover, and the kickstart lever cotter. The gearbox engages all three gears, but the hand change rod, one of it's clevises and some of the tank lever parts are missing. These are all parts that can be made on the lathe which is a good thing, as they are unlikely to be available anywhere.

I'm not sure about this kickstart shaft - it looks much longer than any I've seen...

Carburetter

The carburetter is the correct Amal model 6, with the right float bowl but that's where the good news ends. It's probably in very poor condition as I can feel the air and throttle slides rattling about.

We will have to make some difficult decisions about this. It's an old original carburettor and while you can buy a new 276, you can't buy a model 6. Buying a new 276 would be the sensible option of course...

There are no cables but I do have the remains of the fuel pipe.

Exhaust

The exhaust is there, the plating is poor but no worse than many. The fish tail appeared one day delivered to the railway I volunteer on by a very kind club member. The AA badge is missing from the silencer and the silencer bracket is bent; one or two of the clamps are missing:

Another small issue with the exhaust is that the silencer has been pushed into the bracket - which looks a mess.

Oil Tank & Lines

The oil tank is present, as are all the oil lines and unions. The tank cap is missing, but I am using one that came from Italy on the W/NG for the moment.

Mudguards, Stays, Carrier and Number Plates

The front mudguard and it's bridge were missing. I made the bridge using the W/NG one as a model and the guard has been replaced with a pattern D guard from Feked trimmed to the right length and drilled for stays. The original number plate and it's mounts are there, the front stay is also there as is the front stand - the front stand is pretty rusty and will need surgery.

At the rear, both parts of the guard are there but there will be some welding to repair fatigue cracks. The carrier is there and in good shape, but all the fasteners are missing; the double mudguard stay for the detachable section was missing, but was delivered from Scotland after turning up in the previous owner's stash.

Something that looks a little odd, and it seems to be quite common on these late 20's Ariels is that the detachable part of the mudguard doesn't line up properly with the fixed part - leading to the bike looking as though it's mudguard is too big. This may be something to do with where the stays fit, or whether the stay is inside or outside of the mudguard blade.

Headlamp & Tail lamp

The Lucas H52 headlamp and MT110 tail lamp are both in place; the headlamp is quite battered. The plan is to dismantle both lamps and clean them; I have a sandbag and will knock the headlamp shell back into shape, hopefully the rim as well. The lamp mountings are bent - it looks like the front end took a knock perhaps.

The rim is in particularly poor shape:

The H52 is very interesting - it has no internal wiring, just contacts:

I'm delighted these are all intact.

This is a later number plate. It's clearly an original, but it doesn't have the registration number painted on it - so where did it come from? Perhaps from the previous owner's stash of parts?

Handlebar and Controls

The handlebar, twist grip and both inverted levers are there. There is just enough plating on the bar to show it was once chromed. There are no handlebar rubbers, clips or cables.

I found the Bowden-type clutch lever and the double air/ignition levers from eBay at vast expense.

Dynamo

The dynamo is the correct Lucas E3, and looks to be all complete though I believe part of it's clamp is missing. The drive end bracket has a large crack right across it.

I've realised I don't understand how the dynamo clamping arrangement works - there appears to be some sort of bridge across the engine plates, but haven't seen a picture yet. Something to research.

I'm hoping to get the end plate clean enough to use an adhesive repair.

The chain cover is also there, and will need a weld repair to one of it's feet.

Battery & Electrics

The battery tray and it's clamp are there, though the clamp will need further repair and some nuts turning up on the lathe. There is the remains of the wiring harness attached to the headlamp which looks like it was rubber sheathed; the dip switch, horn button and horn are missing.

The sales catalogue from 1930 indicates that the electric horn option was a Lucas Spartan type so I have sourced a 6 V version and built a handlebar bracket for it. It might be a bit big...

Magneto

The original Lucas KSA1 magneto has been replaced some time in the past with a BTH KC1, so this is probably a period repair or upgrade - the factory despatch record does not mention a non-standard magneto being ordered.

Saddle

The saddle is in place, with all it's springs and spacers - the nose bearing is pretty worn and the cover is missing. I'll make a new cover.

Toolboxes

The toolboxes are both entirely missing. I will make new boxes, learn to work leather and make the leather fronts, and find as many tools as I can. I've started already as you can see from this post...

Next steps 

The policy this time is a refinement of the two stage approach I usually take, that of restoring with no painting or plating followed by commissioning and then repainting and plating. This time it's going to the four Rs:

• Replace missing parts 
• Repair broken parts 
• Rework worn parts 
• Refinish everything

I can't wait to get stuck in!

FH - getting there

 A few minutes in the workshop moves the project on a little bit: the speedo drive locating pin has arrived from the AOMCC gearbox man:

It fits in this hole:

A look at the carburetter reveals that the float chamber gasket is actually there, but that the drip shield is a little distorted and a bit loose, which probably caused the spitting back. The main issue, staring us in the face (and highlighting the perils of long-term projects) is that the carburetter needle is still in the box of bits!

The engine idles now.

By the way, I have changed the 210 main jet to a 260:

A couple more problems are revealed - the inlet rocker oil banjo is loose, and the magneto earth button doesn’t work. The inlet banjo is an easy spanner job; the cutout requires a bit more investigation.

FH - a little more progress, and a big step...

 Well there's been a little bit more progress today. First off, I've finished the second of the finned exhaust clamp bolts:

Secondly I've been talking to people in the club about tyre sizes and whether I can get my desired tyre (Avon RoadRiders) in the size that I want. Having a look at the distance between the tyre and the chain guard reveals around 3/8" to 1/2" but also that this tyre, an Avon SM Mk11, is actually a 325-19. The front tyre, a Dunlop TT100 by the way is a 90/90-19 or 3.60-19. They are both from the 1980's.

I am hoping to buy Avon RoadRider tyres but unfortunately they are not available in the right sizes for this bike. The options appear to be to use a 100/90-19 for the rear (Avon's recommended replacement for a 350-19) and a 325-19 (original size) or a 90/90-19 for the front.

The next bit of progress is very small - it's just a P clip for the front brake cable. I've attempted to adjust both brakes but right now the front tyre is in the wheel clamp.

Lastly and very quietly and secretly I have hooked up the temporary fuel tank to the carburettor and started the bike. Unfortunately it will only start using Easy start, but at least it starts and runs. There may be some problem with the fuel supply or with the float bowl. It runs and returns oil and it runs nice and quietly so now I know that I have the HT leads the right way round, and the oil system is working properly, and the valve timing is correct and the ignition timing is more or less correct though it does spit back through the carburettor.

I think we'll have to wait 'til Monday to have another chance at it, but sleeping on it and looking at some of my pictures suggests that the float bowl gasket is missing. This will give you an air leak in the pilot fuelling circuit...

FH - carburetter

 If any of you recall this post from last year, you'll know that the Huntmaster kit arrived with an Amal 928 Concentric carburetter:

Now that we are getting around to fitting the cylinder head, we'll need to sort out the jetting for this carburetter. A plea to the AOMCC forum revealed that revered Huntmaster rider Steve's FH is fitted with a 626 Concentric with a 200 main jet and a 3 1/2 slide with the needle clip in the middle position.

The difference between a 928 and a 626 is the body size - the 900 series is the larger. The 600 Series comes in 22mm, 24mm, 26mm and 27mm bore sizes and the 900 Series in 28mm, 30mm, and 32mm bore sizes. Presumably a 626 has a 26 mm throat and a 928 has a 28 mm throat; for the record, 28 mm is just over 1 3/32".

As you'll know from this post, this FH is built to Cyclone spec, more or less equivalent to a Road Rocket. Later Road Rockets use a 1 1/8" Monobloc; earlier ones use a 1 1/16" 10TT9 with a 340 main jet, so this 928 should be there or thereabouts but jetting it might be fun. We learned from the forum that Concentrics run about 10% richer than Monoblocs, so we should fit 10% smaller jets and a slide one size smaller.

Standard fitting for the 1958 FH is a 376/12 Monobloc, which is 1 1/16" throat diameter. Jetting is as follows:

• Size: 1 1/16"
• Main Jet: 240
• Pilot Jet: 25
• Needle Jet: 106
• Needle Position: 3
• Slide: 3 1/2
• The carb parts list indicates it uses ferrule 6/132A, which means it doesn't have cable adjusters.

Standard fitting for the 1958 Road Rocket is a 376/36 Monobloc, which is 1 1/8" throat diameter. Jetting is as follows:

• Size: 1 1/8"
• Main Jet: 290
• Pilot Jet: 35
• Needle Jet: 106
• Needle Position: 3
• Slide: 3 1/2

The kit 928 R300 is set up like this:

• Size: 28 mm or 1 3/32"
• Main Jet: 210 (I've got a 260 to replace this)
• Pilot Jet: None, drilling only; apparently 0.0016 (equivalent to size 20) but I understand these can be drilled out and a jet fitted
• Needle Jet: 106
• Needle Position: 3
• Slide: 3 1/2
• It hasn't got any cable adjusters.

Apparently you can fit a pilot jet in the threaded port shown here, on the right & under the bell mouth:

There's an excellent page on the Amal website that tells you all you need to know. It's here, and it revealed that the needle I have is the correct one for a 4 stroke 600/900 series carburetter: