Getting to the bottom of it...

Well, last night we removed the engine again and split the cases. No great problem - oil mess on shed floor.

Not a very good pic I'm afraid. Interesting piece of debris:

It's metallic, the curved edges are as cast and the straightest edge is a fracture. We shall see no doubt.

So the cranks are out; I have started to clean up the front crank:

The timing side journal is good (dimensions shown in the Engine Tolerances page) and the rods look good too. You might recall that No. 1 small end bush is out of position and the oil hole does not line up.

The big ends feel OK, No.1 rocks considerably more than No.4. I will need to grind down my 1/4" BSW socket to allow it to fit the big end nuts - I have already mauled a tube spanner. The oil pressure relief valve had a large chunk of debris in it - rubber or carbon, I'm not sure which at the moment.

Next was the sludge traps. The plugs came out with the impact driver & I consider that a lucky break. Full of carbon though:

However, I poked a 5 mm twist drill into these and the carbon, approximately as hard as clay, was quite easy to remove.

It was obvious from the resistance, and the consistency of the goo coming out that the carbon extended down to the big end oil ways (cross drillings) and no further. At this point, the goo was very oily and no more solid came out.

When I removed the opposite plug, exactly the same sequence of events and when both were clean I was able to poke a bit of welding rod down the drillings, right through the crankshaft. 

It's not a straight hole - they are obviously drilled from either and and meet in the middle.

So, there is not much more I can do with that until I can remove the big ends. Then I can clean out the smaller big end drillings and properly clean the main bore through the middle.

I haven't really looked at the cases yet. When I removed the sump plate ('Very flat, Norfolk') there were flakes of white metal in the primordial ooze. These came from the timing side mains:

I was aware that these were shot from the movement on the nut. Now we have to find someone to replace and line-bore them!

More later.

Shock Horror!!!

To get further into the engine, we have to remove the crankshaft shock absorber. This consists of a sleeve splined to the rear crankshaft and hence driven by it. The sleeve has a external spline as well, and a section of it's length which is a plain bearing surface. The engine sprocket runs on this plain section, and is machined with a face cam. The corresponding cam profile is machined onto a further part, which is splined internally and is driven by the sleeve on the crankshaft.

In order for the crankshaft to drive the engine sprocket, and to prevent the face cams from riding over each other (resulting in no drive) the whole assembly is held together by a heavy spring.

 

Hence if the system is running smoothly, the cams are held together by the spring - but if there is a sudden high torque the cams are free to slide over one another and compress the spring. This thus forms a transmission shock absorber, rather like the rubber cush drives commonly found in more modern machines in the centre of the clutch.

I guess that at the time these engines were designed rubbers were not able to withstand the heat & oil found in the primary drive.

Anyhow, it is all in pretty good shape, with no evidence of wear anywhere. Even the sprocket is good. It has 25 teeth by the way, just for the record. This strikes me as a little odd - Drags list 26T and 27T sprockets; my '52 Ariel Owners Guide says 24 solo and 22 sidecar; the '51 SQ4 parts book lists 22T, 23T and 24T.

Mr Waller however lists 25T, so it must be OK!

The only thing I could find at fault was the retaining nut, which is pretty mangled and the split pin was missing.

Engine Tolerances

Today I have posted a new page, 'Engine Tolerances'. This shows a table of the dimensions and tolerances I am using to inspect the engine, and will build up as I complete the inspection.

I started by measuring the bores. I now know that Amelia's bores are 20 thou oversize, but that they are looking good with little wear.

I've measured up the pistons, rings & pins. The results are shown on the 'Engine Tolerances' page.

In line with a current topic in the AOMCC forum, I will weigh the pistons & pins - though I don't know what I will compare them with! or what I will weigh them with!

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.



Number Crunching

Lest we forget: Cylinder numbering for the four, according to Mr. C.W. Waller:

Next job is to lift the head. We remove the four sleeve nuts inside the rocker boxes; we loosen the twelve nuts around the outside of the head and, using a 1/4" BSW ring spanner especially reduced to fit in a confined space as shown in the picture on the left we remove the final four nuts.

A curiosity here. The front two studs were both fitted with two nuts - one with a regular 1/4" BSF nut, the other with a reduced hex 1/4" BSF nut. One is tempted to think that was to allow a bit more room to throw a wrench around, but I suspect it was more a question of convenience - whatever came to hand. The two nuts were I guess fitted to protect the threads.

In theory, according to the book the next job is to lift the head and place two 1/8" wooden strips between the head and the block, to allow us to raise the head and then to actually remove the nuts from the twelve studs.

The operation will be something like that shown in the picture from the Floyd Clymer Ariel Motorcycle Owners Handbook (3rd Edition) shown as Figure 11 below.

Well, I hope it will. It hasn't happened yet. The head is stuck fast with the adhesion of decades of setting time of a whole tube of Hermetite, by the look of it.

I have taken the hide mallet and waved it around near the engine in a vaguely threatening manner, but I don't plan to do anything else with out a bit more thought and a plea to the AOMCC forum members.

We're back - and it is engine build time.

Well at last. It may be nearing the end of summer, but what better time to get back up and running with the Ariel.

The Bantam is finished - it is now 12 V, and has had it's second engine rebuild. It's just carried me 25 miles around the country south of the city without missing a beat, even through a ford. It still doesn't like ticking over when it is hot though.

The Cyclemaster has been in the workshop for a look over. It is remarkably original as I had thought; it has a coaster brake and is a 25 cc model, but it has been some while with the spark plug loose and is siezed solid. I've put it aside for a rainy day as it's time to get back to the next step with Amelia, building the engine. Regular readers will remember that the gearbox is suspiciously offset, and part of the engine strip will include sitting the bottom end in the frame for an alignment check.

However today, there is not much biking time left. Just enough to make a little start and write a blog post.

So here are some rather grubby rocker covers, taken off for the first time in years, and bringing two of their studs with them.

Here they are again, after a session with some white spirit and a cloth. What I need to do now is source some polishing mops, and some advice on what compunds to use.

And here is what they revealed. Nothing apparently amiss there!

I'm going to spend the rest of the evening relaxing in front of the telly with a book. One by Mr C.W. Waller perhaps.