Wisdom of Years

A silly boy once restored a BSA Bantam and when he came to put on his nice new tyres he thought "those old inner tubes look OK, I'll put them back in". And every week he came to ride his motorcycle, the tyres were flat and he had to pump them up.

The old inner tubes were made from some nice butyl rubber which like most rubber was natively good at passing small molecules through its elastomeric matrix. However as this rubber was very, very old and had become, over the years, very wise, it had learned how to pass the small gas molecules through its matrix very well and was now highly accomplished at the art. 

But, the time comes for us all and after a while the boy realised what he had done and decided it was time to retire the old rubber and he took the shiny new tyres off again, and replaced the 60 year old rubber, with nice new tubes. 

The new tubes still haven't learned how to leak, but the boy has learned not to scrimp on inner tubes!

But for now, dear Amelia sits in her shed with her old tyres and tubes which leak. Since I have no need to remove the tyres just yet, as I want to sort out lots of other things first, I have taken this handy can of tyre weld and re-inflated Amelia's tyres.

They are now full of fluffy goo. I'm told this is not good for tyres you want to keep, since once they are contaminated by the goo they cannot be repaired.

And so now dear Amelia can roll about on hard tyres and sit outside her shed in the sun. Here she is, ready for me to sort out her side stand, and her primary chaincase, and the gearbox.

Isn't she lovely.

How lucky am I..

Ebay can be a marvellous thing sometimes...

Do you know what I managed to buy? at a very reasonable price?

Yes! Its a cylinder head! It has all it's fins intact, it is clean as a new pin, it has new valves & guides, all the threads are helicoiled, both surfaces have been skimmed and there are no cracks!

There is a god... and he lives in Bungay.

Thanks again Draganfly!

Finishing the clutch

Easy job first - degrease and clean the clutch cover. Chrome plate as suspected, with a nice little ding at the front, presumable from someone's boot. Maybe we can beat that out with a handle planishing hammer and a sandbag... maybe not...

Clutch sprocket, plain and friction plates. All jolly nice; friction plates are worn but not burnt. Plate thickness is 1.6 mm/16 SWG, about 1/16". Cork protrudes anywhere between 1/32" & 1/16", so they will need relining. Since they are easily accessible from the outside, and i have 101 things to do, this job will get put aside for a dark winter night.

An additional plain plate, by the way, kindly provided by AOMCC member  & 'Cheval de Fer' magazine editor John Mitchell. Several other parts provided by John are stashed away to appear in later posts.

Next up, clutch basket, repainted by moi, cleaned original needle roller cage and thrust washer, and original pressure plate. John Budgen (John Budgen) provided a new set of rollers.

Here's the centre, which may need to be replaced. I've recut the threads, but as we've seen the splines are not good, inside or out. John Mitchell has provided another. Spring lengths vary 1.625 - 1.64", but since I'm not sure what the factory limits are we will have to see whether this is OK.

I nice set of new set screws for the basket to sprocket flange, with a tab washer - all from John Budgen.

Clutch, assembled and ready for testing. Clutch nuts all ok, spring cups ok, all assembled using my clutch screwdriver, pictured in an earlier post.

Clutching at straws

The clutch has resided at the bottom of the tea chest for almost a year. I think this is the only picture i have of it, sitting on the right of the shot in it's dome. Now I know what it is, it looks like an Ariel clutch though most of the special nuts are missing - but they were soon found in the box of miscellaneous fasteners.

However, since I need to finally face up to the horror that is contained in the gearbox i.e. the long search for a replacement case and mainshaft, I need to get to grips with the clutch and get it fitted.

So dragging it out, what do we have?

Here is the pressure plate, grubby but sound, with all its cups, springs and nuts. All ship-shape & Bristol fashion.

That mangled mess in the background is the clutch centre nut and the tab washer. That is for the bin.  

Here are the plates. One plain plate is missing; the others are mostly OK (no corks missing or horrendously worn) but will relining eventually. The cork protrudes above each plate in the range 1/32" - 1/16" - the plate thickness is about 1/16".

 Hmmm... clutch centre. Ugly.

Hmmm... clutch centre. More ugliness. The splines are very worn and I wonder whether we have a bearing or thrust washer problem that is allowing the centre to rub on the basket screw heads.

Basket/sprocket flange & thrust washers. No evidence of the centre rubbing here? Wierd. Bearing & thrust washers look ok, but most of the needle rollers are missing. Couple of screws missing too.

Here are the pressure plate slots in the basket - not much wear here.

And here is the sprocket. Again, looking good.

Now, we need:

• tab washers
• plates
• needle rollers
• maybe a new centre
• a set of basket flange screws

Let see who's got what...

Back to the gearbox

Eager fans might remember the Gearbox Woes post from a while back, where I was flapping about the fact that the gearbox I had received in the Ariel kit appeared to be the wrong part number, probably from a twin or a VB, and that possibly the casing was wrong and the mainshaft too.

You might also remember that I concocted a plan to test the theory in a dummy build, to look at the chain alignments. Got all that?

Well, now that the engine is in manageable chunks, we can lift it into position in the frame and see if the sprockets line up.

To do that, we have to release the front engine plates since the curve in the crankcases means that it will not drop in from the top. Releasing these plates means that the lower frame rails are no longer tied to the front down tube and the frame is allowed to spring open - not a comfortable state of affairs, so a little support is needed from a box underneath.

With the bottom end in place, we can put all the engine studs back in position and begin to settle the engine & gearbox into position.

We swung the gearbox out of the bottom lug, since we believed that the modification Ariel had Messrs. Burman make for the Square Four was to machine the top & bottom lugs with a different offset. This proved not to be the case, and the gearbox swung back in with not problem.

We know from the parts lists that the Square Four carries different gearbox casing & mainshaft part numbers; My theory is that since the SQ4 uses a 4.00" (WM3 rim) rear tyre, and the twins and singles a 3.25" or 3.50" (WM2 rim), then the gearbox sprocket must be 1/4" further outboard of the centreline, and the mainshaft must be longer to allow the clutch to maintain it's position in relation to the gearbox sprocket. To accommodate the different widths of the tyres, see? If the SQ4 engine is wider than the twins (it is clearly wider than the singles) then the mainshaft must be even longer.

But is it? having put it all back together, we find that the gearbox sprocket appears to align with the rear wheel sprocket (as we had seen months ago) and the clutch journal on the mainshaft appears to sit in the right place in the primary drive casing.

Promising? we need to sort out the clutch to find out.

More later. 

Coming apart at the seams

Well, inspired by Mr. Frank Westworth and his tales of Thor, King of Hammers I have been caressing dear Amelias fine casings and she has finally agreed to show me her most intimate areas.

If you remember, I had released all the head fastenings and had summarily failed to separate the head from the barrel. At the suggestion of the ever helpful Brenton Roy, I released the barrel nuts which of course meant stripping down the timing chest, which all went very well.

So, one lunchtime I took hold of Amelia's head, and proceeded to lightly tap around the barrel base flange with my handly mallet, hide face of course.

Slowly, the barrel came free and I was able to lift it, supporting the pistons on timber bearers as I went. What was revealed was quite happy, as far as I can see - nothing has been measured yet. However, someone has been in there:

As evidenced by the single shiny piston! I'm not sure what is going on there but at least nothing is broken and there is no rust.

On the other side of the joint, again all seems well, but there is a lot of carbon about:

Here's each cyclinder, for the record: Number 1:

Number 2:

Number 3:

Number 4:













Next, we need to get the head off and measure up.

But first, now that we have the engine in manageable lumps, we will go and look at the gearbox again.

Can't stand the pressure...

Now, I have acquired a few bore gauges and this evening I have broken out the trusty old Moore & Wright micrometer and I have measured my oil pump. Here are the dimensions:

• Return bore diameter = 0.499" - 0.500"
• Return plunger diameter = 0.499"-0.4995"
• Feed bore diameter = 0.437"-0.438"
• Feed plunger diameter = 0.436"-0.4365"

Now, seeing as Mr Waller specified 0-1 thou clearance for the singles, I reckon my pump is in pretty good shape. I have max 2 thou clearance on the feed side and max 1 thou on the return.

The drive block is a different story. I have a block that varies 0.561-0.5635"; the 'groove' the block runs in on the feed plunger is 0.573 - up to 12 thou clearance. The return side is better, about 0.570, or max 9 thou clearance.

What do you all think of that? Good to go back in the engine?

I also took the opportunity to flatten the mating face - you will recall there were some little wobbles on the thin bottom edge. All gone now:

Feeling Pumped Now...

Except that, having removed the cyclinder base nuts in the hope that I can lift the cylinder and head together and then knock the head off from inside one of the cylinders, the block still won't shift.

So I try and turn the engine over in the vain hope that compression will break a weak base gasket joint, and then realise that as I have removed the dynamo the primary chain effectively jams the camshaft in place and I can't get it to turn over at all.

So, I must finish the job of dismantling the timing gear and the oil pump.

As I mentioned a day or two ago, the oil pump tab washers are not done up:

Not that you can see them very well in that picture. However, the pump comes off without any drama, though it is pretty tight on the studs. Here's the pump body, nicely marked '51, so it's probably the original. Slightly wobbly surface near the bottom edge:

Here are the plungers, nothing too nasty there. Some wear and light scoring - we will see what they look like with a micrometer on them later. I have nothing at the moment to measure the bores, and I will have to look at what I think the clearances ought to be since the only data I can find in Mr. Waller's book is for the singles.

Lastly, here is the whole pump ready for inspection. The check valve caps seem very stiff and whilst they appear to work I am reluctant to remove them. I really should inspect them and their seats though.



Oily Dynamo

We need to get moving on the engine and we don't have the parts to finish the refurbishment of the dynamo, so we will put them on the list for Drags & move on. Before we reassemble though it makes sense to check everything out.

So, the service manual tells us that the field coil resistance, across both field coils, is in the range 2.6 - 2.8 Ohms:
 

So we set the meter to the 200 Ohm range and short the test cables together, to reveal a resistance in the measuring equipment of 1.3 Ohms.

Now let's connect the field coils into the circuit. This reveals a total resistance of 4.0 Ohms, giving a value of 2.7 Ohms for the field coils alone. Spot on, correct to specification!

Next test - field coils to earth. Should be open circuit, hopefully...

Hey presto, no reading on the meter. Field coils good! Next job, clean the armature & the commutator. Easily done with some solvent, mildly abrasive paper and a razor saw. We'll not attempt to test this since the brushes are in very poor shape and as we said, we don't have the parts to rebuild this beast yet. Continuity tests & earth resistance tests look good though.

 

Here is a view of the brush assembly about to go back in. Clean enough for now, but not clean enough to use. We will finish that when we have some new oil seals & an idea of how this unit left the factory. Black gloss paint maybe? There is no evidence of any paint except for on the end cap:

And here is the drive end. I've re-tapped the hole for the distributor retaining bolt. Fortunately, whoever tried to put a BSF screw in there didn't try very hard and the thread recut nicely. Spare 1/4" BSW screw inserted for now, to be replaced with a stainless one when I can find one. Also, an appropriately sized (but incorrect thread) nut serves to retain the sprocket. Losing it is not an option!

Lastly, tired & oily brushes. Very worn, mangled insulating sleeves, fit for patterns only.